chemistry for energy
TRANSCRIPT
a
A
E11.210 505'
DOCUMENT BESUME
CE C3003-7-7
TITLE Chemistry foi Energy Technblogy II. Energy TechnologySeries.
INSTITUTION, Center for Occupational ResearCh and. Development,Inc.,, Waco, Tex.; Ttchnical,Educaticn ResearchCent:Nrthwest, Waco, Tex.
SPONS AGENCt Office Vocational and Adult Education (Et) ,Washington, D.CA
BUREAU NO 498AH80023POE DATE Sep 81CONTRACT er' 300-78-0551NOTE 250p.: For related doduments see CE 030 771-789 and
ED 190 746-761.AVAILABLE FROM Center for Occupationel Research aneEeveloEment, 601
'Lake Air Dr., Waco, TX 7.6710 ($2.50 per module;$15.00 for entire course) .
EDFS PRICE MF01 Plus Postage. EC Not Availa le from EDES.DESCRIPTORS Adhesives; Adult Education; Behavioral Cbjectives;
Ceramics; *Chemistry; Course Descriptions; Courses;*Energy; Energy Conservation:.*Fuels; Glossaries;Laboratory Experiments; Leaining Activities: LearningModules: Lubricantst; Metals; Nuclear Energy:Plastics: Postsecondary EducatiOn; *Foyer Technology;Solar Radiation; t.T.elinical Education:
)4; *Thermodynamics;itwo'tear Colleges*Corrosion; Electrochemistry
cv
ABSTRACT' '
a This course in chemistry for energy technology is,oneof 16 courses in the Energy Technology Series developed for an EnergyConservation-and-Use' Technology curriculum. Integded'for use intwo-year postseCondary technical institutions to prepare techniciansfor employment, the `courses are.also useful in industry for iTratiingem'ployees in company-sponsored training-prograis. Ccaprised cf sixmodules, the.course is designed with a special emphasis on .allaspects of chemistry as it'relates to the work of an energy .
technician: Basic chemical information and techniques are presented. .
(Chemistry for Energy Technology I is available separately as CE 030773.1), Written by a technical expert' and approved by industryrepresentatives, each module contains the following ielesents:introduction, prerequisites, objective, subject matter, exercises,laboratory materials,'laboratory precedures (experiment section forhands-on po tion) , da tables (included in mostObaslc coarses tohelp studen learn collect or organize data), references, andglossary. Module t leeare Corrosion and Electrocheaistry; Metalsand Ceram modynamics and Thermochemistry; Fuels; Elastics,Adhesives, and bricants: and Nuclbar Chemistry,.(YLE)
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'So
CHEMISTRY
FOR
ENERGY TECHNOLOGY II 4
CENTER FOR OCCUPATIONAL RESEARCH AND DEVELOPMENT
601 LAKE AIR DRIVE
WACO, TEXAS 76710
U S DEPARTMENT OF EDUCATIONNATIONAL INSTITUTE OF EDUCATION
EDUCATIONAL RESOURCES INFORMATIONCENTER fERfCI
This document has been reproduced asrer revert from the person or organizationoriginating itMinor changes have been made to improvereproduction quality
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merit do not necessarily represent official ME
position or policy
"PERMISSION TO REPRODUCE THIS
MATERIAL IN MICROFICHE ONLY
HAS BEEN GRANTED BY
TO THE EDUCATIONAL RESOURCESINFORMATIONCENTER (ERIC)"
2
SEPT. 81'
PREFACE
ABOUT ENERGY TECHNOLOGY MODULES
The modules were developed by TERC-SW for use in'two-year postsecondary technical
institutions to prepare technicians for employment and are useful in industry forup7
dating employees in'hmpany-sponsored training programs. The principles, technIques,
and skills taught in the modules, based on tasks that energy technicians perform, were
obtained from a nationwide advisory committee of employers of energy technicians. Each
modUle was written by a technical expert and approved by representatives *from industry.
A module contains the following elements:
.
Introduction, which identifies the topic and often includes a rationale for
studying the material.
Prerequisites, which identify the material a student should be faMiliar
with be-fore studying the module.
Objectives, which clearly ,identify what the student is expected to know for sat-
isfactory module completiOn. The objectives stated in terms of action=oriented
benaviors, include such action words as operate, measure, calculate, identify4,
.
and define, rather than' words with many interpretations, such as know, under-
stand, learn and a reciate.sp.
Subject Matter, which presents the backgroulld theory and techniques supportive
to the objectives of the module. Subject matter is written with the technical
strident in mind.
Exercises, which provide practical problems to which the student can apply this
new knowledge.
Laboratory Materials, .which identify the equipment required to complete the
laboratory procedure.
Laboratory Procedures, which is the experiment section., or "hands-on" portion of
the module (including step-by-step instruction) designed to reinforce student
learning.
Data Tales, which axe included in most modules for the first year (or basic)
courses to help the student learn how to collect and organize data.
References, which are included as suggestions for supplementary reading/
viewing for the student.
cjlc,ssary, which defines and explains terms or words used within the module
that are uncommon, tectinical,.,or anticipated as being unfamiliar to the stu-
dent.
A
t ,
CONTENTS
Pteface
Table of Contents
MODULE-CH-06 Corrosion and Electrochemistry
MODULE CH-07 Metals and Ceramics
MODULE CH-08 Thermodynamics and Thermochemistry4 /
MODULE CH-09 Fuels
MODULE CH-10 Plastics-, Adhesives, and.Lubricantsti
MODULE CH-11 Nuclear Chemistry.
4 4
f
.
1
'w
;.;
;-:
Arra ingsitic
J.
Center for Occupational Research and Development, 1981
This 'work was developed under a contract with the Departvient ofEducation. However, the content does not necessarily ref het the posi-tion or policy of that Agency, and no official endorsement of thesematerials should be inferred.
All rights reserved. No part of this work covered by the copyrights '-hereon may be reproduced or copied imany.fprm or by any meansgraphic, electronic. or mechanical, including photocopying, recording', taping, or information and retrievals systems without the express 'permisticin of the Center for Occiipational Research andDevelopment. No liability is assumed with respect tetfie use of the information herein.>
.0.
'CENTER FOR OCCUPATIONAL RESEARCH AND DEVELOPMENT
t
J
,i1TRODUCTION
Corrosion is a chemical or an electrochemical proce'ss
in which a metal is- converted to an ionic form, destroying
the metal. There are many familiar. forms of corrosion:
Iron will rust,aluminumaill oxidize, silver will tarnish,
and even chromium plated steel will lose its luster over a
period of time. The damage to metal Objectscaused by corro-
sion amounts to a lossof approximately $10 billion each year
in the, United States. "This does not include the millions
.that are spent in preventing corrosion, such as the $50 mil-
lion spent each, year to, preven automobile,rffriators from ,
rusting. It is estimated that
annually in this country is us
up to 20% of the iron,produced
& to replace ironckobjects that
must be replaced because of corrosion damage.
Much can be done to eliminate and reduce the amount of
corrosion that occurs. The process of corrosion is explained
in this module,,a-s Well as some of qte means available to con-,
trol it In addition, certain aspects ofelectrochemistry
are Presented._
PREREQUISITES =
The student should have completed Modules CH-01 through.
CH-05 of CAVistry for Energy Technology I.
4,
CH -06 /Page 1
I
OBJECTIVES .2.-'C .
c-
Upon Completion of this module, the student should be
able to:
1. Describe the electrochemical process of corrosion.
2. Explain how cathodic protection can be used to protect
a steel tank-or a pipeline from the effects'o corrosions
3. Describe how the activity series or the single elec:
trode potentials can be used to predict the relative
corrosion of metals.
4. Describe some frequently used.cellsp-and batteries*.
5 Define the. following terms:
a, Anode.
b. Cathode.
c. Cathodic protection.
d. Corrosion.
e. Voltaic cell.
f. Electrolytic cell..
g. Electrochemistry. -,0
h. Electrolis% 0)'
6. Describe the elealtrolytic,refining of copper.
7. Describe the importance of magnetite in boiler.
8. List two objectives of bo4er feedwater treatment...,
.
9. List two methOs for removing oxygen from boiler feed-,
water.
10. List four ways to protect metals from corrosion.
e
Page 2/CH-068
A
IISUBJECT MATTER
.,.. ,,
IICORROSION
s
ICorrosion-is/the deterioration of. a metal caused by a
,-. .
reaction with its environment. Corrosion can result throughI
1chemical or electrochemical means. Detrioration by physical
causes is not.called corrosion-but, rather, is described as
galling, erosion, or wear: -Howeverx, chemical and physical
I deterioration may occur at the saMe'time, as in frettingt
cofrosion or corrosive wear. The term "rusting" is reserved
II
for the corrosion of iron or iron alloys with the formation
of the corrosion product iron oxide...
4.
,.. Chemical corrosion is the direct combination of a metal
IIwith nonmetallic compounds such as oxygen or sulfur dioxide.
# .
,Thri type of corrosion is alsO called dry corrosion since
-, water or moisture-is not involved(in the corrosion mechapism.
11 An example of chemical corrosion follows:
Fe + SO2 FeS + 02
Iron Sulfur Iron Oxy endioxide .sulfide
ft
4
Although chemical deterioration is one form 'of corro-.
sion, the pqncipal,type of corrosion involveS an electro-
chemicalprocess. In this form of corrosion a metal is
converted to anionic form with a passageof an electrical'
current. Elecfrothemistry and electrochemicalcbtibsion are
considered in the following sections of this module. ,
s
9 ,CH.-06/Page 3
4
ELECTROCHEMISTRY,
. Electrochemistry is `the field of chemistry concerned"
with chemical changes produced.bY an electric current, and
with the,produttion of electricity by _chemical reactions.
In electrolytic cells'electricity is used to produce desired
chemical changes,'such as in electrolysds of water to :=
produce oxygen and hydrogen gases or in the production of ,
aluminum. In voltaic cells, chemical reactions:areused to
produce electricity, such as in the automobile battery.
E.lectrochemical'processes are,widely used in industry, which
is alargeconsumer'of electricity; therefore, these pro-
cesses are, of importance to' an energy technician.,
ELECTRODE POTENTIALS
.
When a metal such as zinc is. plaCed in water, there is
a tendency far the, zinc atoms to lose,electrons and pass
into solution as zinc ions, as folldws:
Zn Zn+.4+ 2 e--i r
The zinc ions move intothe solution, leaving their'elec-.
trons behind. -The metal, therefore,' becomes negatively
, charged. This potential, or voltage; can be mea4ired;.for
'zinc it is found'to be +0.76 volts when the concentration
of zinc ions is ore molar. This voltage is called Vie
dArd:eieictrode.potential for iincLit is a measure Of the.
tendency of zinc to lose electrons and form ions. By
Page 4/CH-06
1
4/N
k,; to -
S
. f
`omeasuring the standa'rd electrode:potentials f different
metals in solution§ of their ions at a concentration of one
molar, an_activity series may be deVeloped.Table'l gives
the' staftdard electrode potential for a puiber of-metals..
6
f
TABLE 1. ,STANDARD ELECTRODE POTENTIALS.-. .
II
, Element Elect-rode Reaction Standard. ElectrodePotehtial (volts)
Potassium
Calcium
Soditr
Magnesium
Aluminum.
`------.
Chromium
'Copper
Gold
.
.
KK --3..-,.
Ca --,-----*-Ca
++
+Wa ---4-Na
+,+
Mg..----0-Mg4 +3Al -.-: =0-Al*
++-.Zn -:---)i- n
Cr '-'---)i-Cr+3
. +Cu 41-Cu :-
e+- _
+ 2 e,
+ e...
+ 2 e
+ 3 e
+ 2 e-
+ 3 e
+ 2 e ,
+ e.
.:
>,
4°'6,-4
>,-4-
ua'04
vs
o.03
s..
'a'
'
.
.
' ,.
I.
2.93
2.87
2.71
- .2.37
1.66
0.76
0.74
-2'0,34
:1.68
.
.
.Au --L---Aw Au+:
7--.
Table 1 is often carled the_electromotive series, or
activity series. The metals at the -nip of Table 1 (such es
potassium) are,v'ery 'reactl,ve, whereas the metafs lower in
Table 1 (such,asgold) are more stable. -GOld, can be youdd
in natureowp the, elemental State, whereas potassium cannot:
The reduced form of any element will reduce the oxidized form-,
of any element below it in the series. For example; metallic
.*
1 CH-06/Page 5
c
1 zinc will reduce copper (II) ions according to the following
reaction:
Zn + Cu t+ Cu + Z.n++
This reaction is utilized in a voltaic cell, called the L -
Daniell cell, in order "to produce electricity. The wltage
of the cell is foUnd by subtracting (algebraically the.-
potential of the copper. electrode -from that of the zinc
electrode. The voltagesaxe given in Table 1.'
Cell voltage = 0.76 - (" -0.34)
= 0.760+ 0.34
= 1.10-volts'
endard electrode potentials, abbreviated E°., do not
taker
into account changes,in concentration. As.was pre-.
.viously stated, the standard electrode potential's are found
by measuring the-, voltages in al, cell with a one-molar concen-,
- tration. The Nernst-equation makes it possible to calculate s'
yoltages at other concentrations. The-Nernst equation for a
cell at'ZS°C is as folloWs:
E E°Eas9
loMolar concentration of prodUcts
= gMolar concentration of reactants.
Page 6 CH-06 12
Equation 1
I'
t
here: .
I.
.
.,:j = The voltage for.the .cell.
E° = The standard electrode potential (from Table 1).
In = The number of electrOns involved in the teactiqn.
EXAMPLE A: VOLTAGE MEASUREMENT.
Given:
Find:
A 0.1 M solution of ZnSO4.
The voltage of a strip of zinc immersed ii the
solution -.
Solution: Zn Zn" + 2 e-
(The value of 1 is assigned as the concentration
for all elements.).
E.='e -
= 0.76
= 0.76
= 0.76
0.059 Molar concentration of productslog
n Molar concentration of reactants
0.05.9log
0.1T(0.0295) (-1)
+ 0.0295 .
E =- 0.789.
Although standard electrode potentials are useful for
predicting the corrosion of metals, other factors are impor-
tant. Some metals display anxunusuak inactivity called
passivity. Pdssivity can be considered to. be the. reason a
metal does not corrode when it should according toits
darj/electrode potential. FqT example, accordingto its
standard electrode potential, one would expect aluminum to
be a very reactive metal; yet, it possesses good corrosion.
139
CH-06/Page f
resistance. AluMinum quickly forms a surface coating of
aluminum oxide,'which stops further corrosion. Ina addition,
chromium should be more reactive than iron (according to
their electrode potentials). However, chromium actualli is
used to protect iron (Steel) from corrosion in irplications
such as chromium-plated automobile bumpers. Passivity is
usually caused by the formation of thin, adherent metallic. 4
.Oxide%Foatings.
ELECTROLYSIS
5lectrolysis is the process in.which electric current
is passed through a solution of ions to produce desired
chemical reactions. Electrolysis of a solution of sodium
chloride in water is de-
picted in Figure 1. When
sodium chloride, NaC1, is
dissolved in water, the
ANOD t fCA NODE 'solution will contain
012 ,H2 hydrogen ions and hydrox-t,, t
b*its+ ide ions from the water,9!t'fi,a*
5
sodium and choride ions
from the sodium chlorine,
"-and many molecules of water.
When two electrodes (com-
posed of an inert mate ial
.such as graphite) are
4
1 1
BATTERY
I
SNaC1 soLunoN--
Pigure 1. Elqctrolysis-Aqueous Sodium,plori
1
placed in,the s,olution and connected to a battery, the nega-
tive ions (C1- and OH-) move toward the positive electrode,
called the anode, wherk-they may lose electrons and be oxi:
diz0. The.possible oxidation reactions are as follows:
Page 8/CH-06
2 Cl C12 + 2 e-
2 H2O 02 +, 4.H+ + 4 e
, One would expect that ch=lorine gas, C12, or oxygen gas, 02,
would be'emitted at the anode. Chlorine will be produced
in a concentrated solution of sodium'chloride. The positive
ions (1-1:- and Na+) migrate to the negative electrode, called
the cathode, Where they may gain electrons and be reduced.
Possible reduction reactions at the cathode are as,folloWs:
Na+ + e
2 H2O + e 7 " 0 ' H2 + 2 OH
Water'is more easily rOuced than sodium ion; therefore,
hydrogen gas is produced at the cathode. The net overall-
reaction for electrobr'gis of aqueous sodium chloride is
obtained by adding:the two half-reactions as follows:
2 H2O + 2 e H2 + 2 OH
2 Ci- C12 + 2 e
2 H20+ 2 C1 H2 + C12 + 2 OH
The hydroxide ions, OH, combine withsodium ions, Na+, to
form sodium hydroxide. Electrolysis of aqueous sodium chlo-
ride is an important commercial process for production of
hydroge4 chlorine, and'sodium hydroxide.o
CH-06/PAge 9
15
O
4P
Another example-of the application of electrolysis to
commercially produce chemicals is the electrolysis of an
aqueoui solution of sulfuric aci,d. Sulfuric acid, consist-
ing of hydrtgen ions and sulfate ions; does not decompose
during the electrolysis process. The following reactions
occur:
2 H2O 02 + 4 + 4 e (- at the anode)
4H+ + 4 e 2 H2 (at the cathode)
2 H2O 2 H2 02 (net reaction)
The net reaction shoWs that water is decomposed by the elec-
tric current into hydrogen and oxygen gases. ThiS method
gives very pure hydrogen and oxygen. However, it is expen-
sive, and its industrial use is limited to'conditions where
purity of gases is important such as in the production of
dxygen. for breathing purposes.
ELECTROLYTIC REFINING (METALS)
An important application of (electr..ochemistry is electr60
lytic refining of metals: In this process, impure metals
are converted to highly, pure forms of the metals. Copper
an important metal'i- is refined on a large scale by electro-
lytic methods. The primary use -of copper as electrical wire
tequires,a metal of,M1fi'puisity.,. which can be obtained
through electrolytic refining. Gold, sili/er, nickel, lead,
and zinc are successfully refined by electrolysis 6f AqueoUsa - ,
a
Page 10/CH-06
16
01
, it 7
4?
+In
solutions rand aluMinum is produced by electrolysis of a
fused (melted). sblution. The main advantages of electrolytic
refining- are:
greater purity'of the primary metal
. and recovery of by-product metals (especially
precious metals). -
By-product metals are present in very small amounts: In
electrolytic refining, an impure form of the Metal to bee
refined (such as copper) is made the anode; and it is us-,
pended in a suitable electrolyte (as in Figure 2). The
anodic reaction is therefore, Cu o Cu++
+ 2 e . A thin
CATHODEANODE
Cu2.2f-Cu Cu -Cut.2*-
*Figure 2. Electrolytic Refining of Copper,
7
t.
CH-106/Page 11
sheet of the pure metal is made the cathode; The cathodic
reaction is Cu++
+ 2 e .----0Cu. The conditions of concen-
tration and teuerature are carefully regulated so' that the
deposited metal has a highpurity.° The less active metals
(such as.gold and silver, which are found in impure copper)
do not dissolve; they fall to the bottom of the electrolysis
cell and.form a'mud or slime',from which they are recoveredi
LAW OF ELECTROLYSIS
In 1832, Michael F raday-disdovered that the quantity
of substances undergoi chemical change at each electrode
during electrolysis is directly proportional to, the, quantity
of electricity that passes through the electrolytic
Experimental results show that one electronxedutes one
silver ion; whereas two elettrons are required to reduce
' one copper (II) ion, as follows:
a
Ag+ e Ag
r A,u + +, 2 e-
Since one-0electron is,required-10 reduce one Ag
+, and two
electrons are required to reduce one Cu + + , it follows that
Aone mole of elecvnins is' required to reduce one mole of
silver ions, and two moles ,of electrons are required to re-
dUie one mole of copper (II) ions. The electrical-charg*
of a mole of electrons, called a "faraday," is equal to
96 p500- coulombs.
Page 12/CH-0618 ;
1 Faraday = 6.023 x 1023 electrons
='1 mole of electrons
= 96,500 coulombs
A coulomb ithe quantity of electrical charge passing
through a given point in the cell in one second,, at a cur-
rent of one amppre:
Coulombs = AmpereS x seconds
7 EXAMPLE B: WEIGHT CALCULATION,..USING LAW OF ELECTROLYSIS.
Given: A cathdd4c reduction of .copper (II) ions,
:during which 1,60 amperes of current passes
for one hour.
Calculate the weight of copper produced.
Solution: Coulombs = Amperes x.seconds,
= 1.60 amps x 60 min/hr x 60(sec/min
= 5760'1
96,500, courontbs will reduce-63.54 = 31.77 g
576G5760 coulombs will reduce 31.77 g x
96,5001.89 g of
copper
I
L94
CH-06/Page 13
I
R)LECTROCHEMICAL MACHINING
\k,
Electrochetical machining (milling) is becoming more and
morevimportant in that it is replacing mechanical machining
of complex designs in metals. The process is ?llustrated in
Figure 3. The metal to be
ELECTROLYTE 'machined is made the anode,
and the piece that deter-OBJECT
mines the filial slTpe (die),g.
is mate the.cathoae. The
current is largest where
the two electrodes come in
closest contact. As a re-
sult, ,the most metal :is
Q2 in. SPACE f removed from the object
where the die cqmeS'closest
'to the material bping
Figure 3. Electrochemical formed. 'Thus, the'- object
Machining. being machined gradually
takes the shape of the die.
'The electrblyte, usually a 5 to 10i solution of a salt,
is passed at high velocity through the gaps between the ob-
ject bding machined and-the die in order to keep the parts
cool-and retev*.the electrode reaction products. 1The cathode
reaction at the die4-is. the evolution of hydrogen, ;rather than
the plating of a metal. Current densities used in electro-
chemical maohinipg -are high (1000'to 1500 amp/ft2) and
voltages are low,(less than 20 V). Under these conditions,
the removal rate for aluminum, tungsten, titanium, nickel;..
iron, chromium,,and Copper is about two cubic centimeters ,
per minute., DiectrkhemicL milling or machining is usecCtol .
shape complex parts used in automobile transmissions-. One
Page 14/CH-06
4
20
I
1
1
a
I;
. -0
Oa
advantage of electrochemical,machining is that the product
d6es not have the stresses that ai-e,4-el.ways'present in mechan-
ically machined parts..
VOLTAIC CELLS
Voltaic cells; also called galvan-ic cells,' produce an
electrical current through chemical reactions, These cells
may be primary or secondary. Erimary!cells cannot be re-.
Charged, whereas secondary cells can. The most fAmiliaf
primary voltaic cell is the., dry cell. (This cell is not
actually dry; if it were, it could not conduct a current.)
The electrolyte consists of a thick pasteaste of ZnC12, NH4C1,
and,Mn02. The center, positiveIole-is made,of'graphite,
and t e contents are sealed inzinc, which Ctt as the
nega ive' poleof the cell. Zinc, which has a higher elec-/
trode potential than carbon, supplies the electrons that
flow from the zinc to the carbon pole_jigure 4).. The
followingreactionsoccur, attheanode and cathode:
Zn, >Zn++
+ 2 e (anode)
2' NH4+. + 2 NH3 +.11'; (cathode)
4
Zn + 2 NH4- Zn++
+ 2 NH3 * H2 (net cell reaction)
The ma,nganese dioxide tn'the cell qxidizes the hydrogen as,
it is farmed inorder to produce water. Otherwise, the hy-
dr,ogeft gaswould accumulate on the cathode anestop the
action of the cell.
21
0
CH -06 /Page 13
Cs
O
Ax
ZINC CUP ANODE
r.
GRAPHITE eiTHODE
MOIST PASTE sui,.*OF NH4 Cl 0
c;Mn 02 CARBON
01
Ftguv 4. Cross-Section'of a Dry Cell /--
.
A secondary vplaic cell is onethat.is reversible, ,
(that is, it can be,re6harged). The,most common battery is
the lead storage battery used in automobiles. A battei)r is.-
a comblnation of two or. more ceals in an assembly. The 12-
volt aUtomobile battery consists of siX,celrs, each of which
supplied two volts. The cathode is composed'of lead dioxide,
..Pb02, and the anode is composed of lead; Pb. Both anode'
and cathode are'immersed in,a sol4tion of sulfuric acid,
with a density of approximateIy,1.30 t/cm3. °A 4rdrome,ter
can be, used to readily determine 'the tondition of the bait?
tery. When the-density of the sulfuric acid falls below
1.20 g /cm3, the battery needs redhargirig oireplacing:* The
electr,pde reactions that occur during discharge o the bat-*
tery'are as f011ows:
. 6 .
Pb + e (anode)
Pb02-, + SO4 2 + 4 H+ + 2 e PbSOL; 2 H20 '-(cathode),
Pb + Pb02 + 4 H+
+ 2 504,--=--2--31-PbSO4 + 2 H20 'cnet reaction)
Page 16/CM-00.
fire
22r
c
40,4
As can be seen from the net reaction, during discharge,lead is consumed through conversion to lead sulfate. The
- .sulfuric acid also is consumed through conversion to leadsulfate and partially_to water which is the reason for
.. the decreaseAn density of the sulfuric acid solution as:the battery discharges. During recharge, the lead and sul-
,
furi-C. are regeneiatek. A *discharging, cell is depicted- inFigure ,5.
Figure 5.1 Discharging Lead-' Acid Storage Battery.
r
Pb0 PbIt)
4
DISCHARGING 'CELL
tip
ELECTROCHEMICAL CORROSION'S
In electrochemical corrosion., a metal, is converted toan ionic form in the presence of water with a passage ofan electrical current. Corrosion of iron is depicted inFigure 6. . ":
err
I
CH-06 /Page 17
J
1
, AIR
CATHODE
IRON
WATER
-ANODE
O
Figure 6. Corrosionof Iron.
One region on the surface of the iron serves as an
anode at which the iron is oxidized:
Fe++
+ 2 g- E° = 0.44 volts (anode)
The electrons produced at6the anode migrate to another
region on the surface of the piece of iron where they are
available to reduce oxygen accordirig to the following reac-
tion:
+ 4 R+
+ 4 e 2 H2O E° = 1.23 volts ".(cathode)
Corrosion is enhanced by the presence of salts or other
ions,. which assist in carrying the current through "a moisture
coating. This enhanced corrosion is evident on automobiles
in areas where there is heavy salting of roads during winter
to remove ice and snow. Ultrapureiroh is not very suscep-$
t-ble to corrosiorrbecause the anodic and cathodic 'sites are
Page 18/CH-06
2 4. '
)
1,-: , .
'EN4.' ; .
ia
not available; however, ordinary iron has impurities or
defeCts which can become cathddic or,anoslic..sites., allowing
-electrochemical corrosion to proceed. Even stress ili/oduced
during theaanufacturing process can provide an environmentr
for corrosion.
BOILER CORROSION
N.
,Boilers are,widely used to. produced steam which maN.be
uS-e-drtb-tenerate eleCtricityyprovide 5gace1-e-at-i.ng, or pro:-
vide heat for industrial processes. Corrosion°of boilers can
occur.on the water side of the'boiler that is, inside the
boiler tubes, the superheater, and,condertsing equipment.
Corrosion canalso occurrbn-the heated (fire) side'of the
equipment. High pressure boilers,that drive steam turbines
operate on a recirculatory system and use "make-Up" quanti-
ties of water that has been carefully treated. Low pressure
boilers that provide hot water or.prodess steam often use
less of this treated water.a
Boilers are constructed..of a low-carbon (mild) steel
or lbw-alloy steel. -At temperktures above 250°C,. water
attacks steel to forM'a'.surface layer of magnetite (Fe304),
according to the follOwing reaction:
3 Fe +.4 H20- + 4
1h
c
4_ a
25CH-06/Page 19
)
--Themainetite.film is -h-i-ghle since it protects the'steel from further 61d4tion. The growth of the protective
t)agnetite film inside a tOiler is accelerated by using alka7
line boiler water,,whereas exc7ssive acidity removes the
. film. Therfol-e, boiler water is usually maintained at a .
pH betwen 8,5 and 9. The proteCtive magnetite film is also
weakened by oxygen in the boiler feedwater", causing the cor-t.N
rosion,of the underlying steel. Oxygen is commonly removed
by mechanical or chemical rhethods,.
Condeni.ers and heat exchangers, are made of copper,
brass, bronz and copper-nickel'alloys. Cooling water used
with ,condenSerg and heat exchangers normally is untreated.
This water may vary. from fkarly pure river, or lake water
highly polluted water from ;harbors and bays. The pollute.
waters often contain hydrogen sulfide, causing rapid deteri-.
oration of copper and its aloys., The primary means of limit
ing corrosion in condensersand heat exchangers is through
careful selection-of the materialS of construction.
WATER TREATMENT
Themain objetctives ofjeedwater treatment are,the
prevention of corrosion and the prevention of scale 'forma-,
tion. This scale, Whi.Ch ism deposit of Calcium carbonate'
and magnesium hydroxide On the metal surface, 1.5 a poor
t-
conductor of-heat and interferes with the-normal'heat trans-
'\fer in the boiler. Scaling can cause a larA increase in
the operating, costs of boilers. If steam is,iised for power
concentrations of silica and silicates in feed- _
be reduced in order to minimize the-volatilfza-
with steam ich can 'cause formation of damag:
b des. .-;
production
waters mus
iion of Si
ing deposits on-turbine-.
Page 20 /CH -0626
-
Water hardness (that is, the concentration of calcium
and magnesium ions) is reduced.by precipitation, distilla-,
tionor ion- exchange. The addition of lime and soda is .
used to precipitate the calcium as carbonate and the mag-
nesium as hydrokide. This procedure Willreduce the water,
hardness to 10 ppm or less. Water can be distilled to 're-
move calcium andmagnesium ions. Distillation can reduce
the dissolved solids to 0.1 ppm. In the ion-exchanger
method, synthetic ion-exchange res -ins remove'the calcium
and'magnesiuM-ions, replacing them with less harmful ions-
such as sodium pr hydrogen ions. The ion-exchangemethod;
often called "polishing the water," is very effective. By
proper' cont-coi of Water hardness, the formation of scale in
boilers can largely be eliminated.
Oxygen removal from boiler feedwater is importa4t to
control corrosion. This removal may be accomplished by
mechanical.br chemical methods. The oxygen, along with
carbon-dioxide, can be' removed mechanically by spraying pre
ated water into an evacuated chamber. The oxygen content
of boiler feedwater can also, be reduced (to about 2 ppm) by
storing it for 30 minutes at a temperature just below boil-./
ing.
For use in high pressure boilers, water should have an
oxygen conent less than 0.005 ppm. Treatment with hydrazine'
can be Used to accomplish this !oxygen reduction according' to
the following reaction:
N2H4 N2 2 H2O
27
CO
A
CH-06/Pag6: 21
O
Some of the hydrazine is decompose by heat to form ammonia
and nitrogen. The ammonia is use 1 sinc- t reacts with
CO2, thereby removing the C fr the ater. Another chem-
ical used as.an oxygen "scaveng- is sodium .ulphite.
Sodium sulphite reacts with oxygen according to thefollow-
ing reaction:
2 Na2S03 + 02 -----4'2 Na2SO4
One digadvantage of using sodium sulphite to remove oxygen
is the formation of sulfates. These sulfates can react with
free Calcium ions to form scale. Still another method of
reducing the Oxygen content of boiler water is with an ion-
exchange resin. This method can reduce the concentration
of oxygen to less than 0.01 ppm.
As.indicated earlier, it is desirable,to maintain the
pH at a value of 8.5 to 9 to ensure that a protective
layer of magnetite is formed and..maintained.- This requires
the addition of chemicals to raise the pH. Ammonia, cyclo-
hexylamine, or morpholine are commonly used for pH control.
Amines may also be usedto form a protective film over the
metal surface. Octadecylamine is the most commonly used
filming amine.
APage 22/CH-06
ti
28
I
I
PROTECTION OF METALS FROM CORROSION
Several widely used methods of protecting metals from
corrosion are listed below:
CathOdlc_p_rotection
Metallic coitings-, such as from galvaniiing or
ele5troplating
Tholwnic coatings, such as phosphates
Organic coatings, such as paints %.4
Underground pipelines or tanks are often protected by a
cathodic protection method which makesthem similar to
cathodes in a voltaic cell. 'A more active metal, such as
zinc or magnesium, is buried adjacent to the pipe or tank
and connected by means of a wire or cable. The active metal
is converted to its ionic form (rather than the iron in the
,pipe), thereby protecting the pipe. For co ntinued protec-
tion, the sacrificial anode can b replaced at intervals.
The protection of an iron tank from orrosion using'a sacrifi-
cial magnesium anode is depicted in Figure 7.
A
0
Figure 7. CathodicProtection of an
Iron Tank.
e
TANK
Mg
A similar type of protection is given by the procest
known as galvanizing. In this process, a thin coating of.
zinc is applied'to the iron object. If this coating is
broken; allowing moisture and oxygen to contact the exposed
iron, the remainder of the zinc acts as a large anode, at
which oxidatiodoccuri more readily than at the iron surface.
Phosphatizing is a common method for corrosion preven-
tion. First, the surface of the metal is grit- or sand-
blaste4,toclean and roughen it. Then, the article is dipped
in a phosphoiic, acid-phosphate salt solution for 5 to 50
minutes. Sincethe phosphate coatings created in this Pro-.
cessare very adherent, they prevent electrical` conduction
along the surface of the'metal. Phosphate coatings are often
coated with paiht to farm an effective torrosion barrier.
The process of applying a thin coating of metal to some
article when 'immersed in an-electrolyte is called electro-
plating. Generally, the article to be plated is another
metal:but plastic's are also_plated. Many knobs in. automo-,:;
bales are made bf chromium-plated plastic because plastic is
less expepsive than, metal and it also reduces the weight of
the-knobs. Four advantages of electroplating ar ito. as follows:
1. *Ceap metal objects are coated with an expensive metal-
(like gold-or silver) to increase their value or improve
their appearance.
2. Metal coatingt of nickel or chromium are used for their. .
decorative=ffect or for combining improved appearance
withtincreased wearing qualities,.
3. Zinc plating p tects other metals from corrosion.
4. Chromidm prating f bearings in machinery greatly in-\ _
creases their ability to withstand mechanical wear.
Page i4/CH-06
-
Some metal plating is conducteier d without an electric
current. This type of:plating process is called immersion,
or electroless,prating. A specially formulated bath that
has phosphate and nickel in the Coating is used to plate
electroless nickel. This coating is extremely hard and
wear-resistant. Much gold plating (especially of jewelry)
is conducted by'dipping the object to be plated in an elec-
.trOlyte containing gold ions. The amount of metal depositpd
can be,controlled to some extent by the length of the immerL
sion. The metal object to be plated is usually made of brass.
In electroplating, the object to be plated is made the
cathode, and the metal to be plated is supplied by the elec-
ttolyte. In some processes, a bar of the metal to be plated
out is used as the anode. This type of arrangement serves
to keep the concentration of metallic dons in solution con-
stant.__Jhe object to be plated must be properly prepared
prior to electroplating.
The selection or a proper material for a given applica-
tion is all- important. The corrosion-resisting property of
alloys is often far superior vo pure metals. An important
consideration in the selection of proper materials is t
make certain that metals that have widely differing activ7,
ities'are not placed in direct contact with each other. For
example, steel bolts should not be used to fasten brass
plates since the "battery" formed will cause severe corrosion.
a
31CH-06/Page 25
4.
LABORATORY MATERIALS
Laboratory 1 Laboratory 2
Clean, bright° nails Test tubes
Test tubes Small funnel40
0.1 M NaOH Stirring rod
0.1 M Na2Cr207 Bunsen burner,
0.1 M NaC1, Calcium sulfate
.0.1 M HC1 Magnesium sulfate
0.1 M KOH o Sodium carbohatl
0.1 M Na2CO*3 Lime-water
0.1 WKNO3' Distilled water
0.1 M HNO3 So p solution*(40 ml of liquid
0.1 M Na3PO4, soap in 160 ml distilled
0.1 M KSCN water
0.1 M Na2C204 250 ml graduate
0.1 M H2SO4 Aluminum sulfate solution'
ph, paper. (20 g/liter)
Test tube rack Fine clay
0.1 M potassium hexacyano-
ferrate, K3Fe(CN)6
0.1 M iron (II) sulfate
Agar
Burner
it phenolphthalein
_* indicator
Petri dish
Copper wire
Zinc strip or mossy zinc
Page-26/CH-0632
4
A
1
LABORATORY PROCEDURES
LABORATORY 1. CORROSION OF IRON.
-Corrosion is a complex p 'rocess in which a metal is
converted to its oxide. For exmaMple, iron corrodes to..
4
orm iron oxide as follows:.
4 Fe + 3 02 2 Fe203
Many factol\s"influence the rate of corrosion of iron, such
as.the presence of salts, contact with other metals, and
the pH of the solution. Iron will not rust in water unless%
oxygen is present. On the other hand, iron will not rust1
in a substance such'as oil if there is absolutely no water
present even if oxygen is present. Each year,corrosia'
'of.iron costs industry in the United States billions of dol-
, ,lars. It is estimated that 20% of the iron produced
,.ahnually in this country is used to replace iron objects that
have been discarded because of.excessive rust damage. In
this experiment; some of the factors involved in the corro-
sion of iron are investigated. i
PROCEDURE'-r
ICarefully record all data in Data Table 1. ,
1. Put a small, clean, bright nail in each of,,13 test tubes..
. Hold the iest,tube at an angle and gently slide the nail
into the tribe to avoid breaking the tube.
1
33
..,
CH-06/Page 27 .
It
N
I
2. Using the reagents listed in.Data Table 1, fill each'of'
the tubes with enough liquid just to cover the'nail.
All thesolutions:(except water),should be 0.1 M.
3. For each solution:determine whether it is acidic,
basic, or neutral bjr using litmus paper. Record find-
ings in Data Table 1.
4. Leave the nails in the solutions overnight. Observe
and record any changes that have taken plaee.
5. To test for the presence of'iron ions (Fe44.4) in the
solutions, add'sever drops of 0.L M potassium hexa-
_cycanoferrate, K3Fe(CN)6, and record any observations.
In some cases, a metal in contact with iron will 'cause
the iron to rust, much faster than it would without being
ingcontact with the metal. In other cases, the iron is ,
protected because the second metal corrodes, in prefer-
ence to the iron. Ivignesium is often. used to protect
iron tanks in a process called cathodic protection.
6. Prepare about 100 ml of agar mixture by heating 100 ml
of distilled water to its boiling point,*removing it
from the burner, and stirring in one gramof powdered
agar. Heat again until the agar is evenly dispersed
throughout the solution:3
7. Add 10 drops of 0.1 M potassium hexacyanoferrate and
10 drops of 1% phenolphthalein indicatft to the agar
mixture, and stir thoroughly.
Place one nail on one side of a petrii dish. Ben
another nail sEa'rply with a pair of M.iers and'p ace
it on thp other side of che. ish. Do not let the
nails touch each other. S:
Page 28/CH-06 34
---
vi
,4,-
1: 9. -Twist -a clean piece of copper .wire around a. third naitl:4.
.
I(1f the copper wire is not bright and shiny, or if it_
has a coating, sandpaper-the Wire until thecoating is
Iremoved.) Place t4s nail in -a second petri dish.' -
, :.
110. Twist a clean piece of zinc metal -af-5Up-d-7-a fourth nail-;
and place it in tire_ second petri dish with the nair,
,wound with thecopper Wire. Do not allow the nails to.
., if
I.
touch 'eadh other.'
11. When the agar mixture has cooled, but while it is still
a liquid, pour it carefully into the petri dishes until
the nails and attached metals are covered.
12. Observe the nails during the class period and the next
day. Record any observations in'Data Table 1.
ti
Er
LABORATORY 2. PURIFICATION OF WATER.
elb
This experiment investigates the differences between
soft water, hard water, and permanent hard water; and it
determines the effect of these waters upon'a soap solution.
It also investigates the use of alum'to purily water by
coagulation.
PROCEDURE
Note: =Ordinary soaps are ''sodium salts0of complex
.organic acids. Sodium stearate (NaCI8H3i02) is present in
marry common 'soaps. (... 1
IP
35. . .CH-06/Page 29
9
Et.
4
1'
1. Add a-drop or two of-soap solution (40 ml liquid soap'.
in 160 ml distilled: water) to a tiest tube h
with- distilled water, andshake'the'tube% Are lasting
suds producld? Distilled Ater is-"softwater," and
the results are characteristic, of these waters.
2. Add a drop orwo o'f'soap sol9tion to a- test tube half,
filledith-tap water, and shake the tube. Is the tap
-water soft water? (Tap 'Water varies in different lo-.
calities; it may range from very soft to very'hard.) 4
3. Place a-small amount of agnesium.sulfate into a test
tube half filled with .distilled water: Shake-the tube
fto dissolve themagnesium sulfate.' Add a few drops-o. .
the so p solution and shake the -tube. Do.suds form?
The precipitate that is formed is magnesium stearate.
Water that gives precipitates witir soap.solution is
called "hai'd water."
4. Contihue adding soap solution'and shaking the tube
until permanent suds form. Enotigh soap solution must
be added until all the magnesium ion is removed. Why
does/it cost more to wash with"-hard water than with
soft water.
S. Make another test tube of hard water by adding some
magnesium sulfate to a half-filled test tube of dis-
tilled water.
6 Boil the waterin the test tube.
7. Add a few drops of.soap solution. Do lasting suds
form? Did the boiling of.the water affect its hard-,
ness?, A hard water that is not ,softened by boiling
is known as a "permanent" hard water. .These waters
usually contain magnesium or calcium's fate; they
cannot be softened by heating, but the may be softened
by adding a solutiofl of sodium carbonate.-
$
Page 30/CM-#66
36
44
.8. Mal9e a test tube 6f hard water by adding some calcium
sulfate to a half-filled test tube of ditilled
Shake the mixture and then filter it into another test
tube. .To the clear filtrate ,
add a4solution of sodium car
bonate as long as a precipitate continues to form.
10. ,Filter, then add some soap solution to the filtrate.
Was the addition' of the sodium carbonate-solution
effective in -Softeninsgthe hard. water?.
11. -Add some calcium bicarbanate to a half-filled test tube
of distilled water.
12 Test this solution for holiness,/ I,s.the calcium bi--
carbonate solution hard or soft?"
13. Make another test tube of calcium bicarbonatesoliition
and heat it until it boils.
14, Filtey the-solution "and. test the' Filtrate with a-few,
.drops of soot) solution. ,Has jthe;wat:ef 'Solution of
calcium bicarbonate been softened? This type of bard,;
water is called a "temporary" hard water: Temporary,
hard water can also be softened by .the addition of
lime or lime water.
Note: The following steps concern purification of
watertby coagulation.
15. Make 25 ml of a dilute solution of aluminum sulfate,
Al2(04)3°
16 Ad&50 ml of lime water. The reaction is as follows:
Al" + 3 OH Al(UH)3
rDescribe the precipitate of aluminum hydroxide formed.
'CH-06/Page 31
17. Add water to a graduated cylinder until it, is approxi-.
.1 mately. two-thirds fully Add some fine clay and stir.
18: Add 10 ml of aluminum sulfate solution and mix.
19: Without stirring,'slOwly add 20 ml of lime water.
20. Allow the water to stand and obser+e'from time,to time.
Aluminum sulfate, or "alum" as it is called, is commonly
used as a flocculating agent in water 'treatment. When alum
is added to water, aluminum hydroxide forms as a spongy,
gelatinous, precipitate. The aluminum hydroxide precipitate
has an overall positiVe charge. Since most of the suspended
particles -(such as clay) have a negative.:charge, the sus-
pended particles are.attra*ted to _the precipitate of alumi-
num hydroxide and are carried doWn with it. In this way;
almost all finely divided matter is removed from the .water-.
0
1
Page 32/CH-06
,
tr
38
0
1
.
DATA TABLES
DATA TABLE 1. CORROSION OF IRON
. -
Reagent ',
. pHReaCti011(yes or no)
N
Iron Idh .Present(yes or no) '
.
KOH, .
.
.
..
.
.
.
NaOH..
.
NCL .
,
. * ... $.
..
HNO3.
. ''
"'. . .
H2SO4 e
NaC1 .
,..
.
.
..
110___
.
Na2Cr207 '... .
. c .. .
Na2C0.3
,
._
KNO 3.
..
..
Na.'004 *. «
.
., .
r -.4.--
'qqa2C204*
' .a
KSCN
. Water .
,
\_,
.
.,
.
..-
a, The first two .reagents above are bases, the next'three
are acids, and the remainder are salts. Are any regu-
laritics obsqrved in the corrosion of iron in the pres-
ence of the solutions?
, .
,
, . .
. .. .
._.
.. -i.
..- "
4
CH-436/Pige 33
;2:
Data Table 1. Continued.=116
-
F
-b. Reco;,,d any observations c dcirning the iron nails in -,
the agar mixture:
(4 Straight nail:
(2) Bent nail:
c. What effect does stress (placed in the nail by bending)
have on'the'nail's corrqsion resistance?
(1) COptter woun
(2) Zinc wound nail:
A coating of zinc is often placed on iron to f rm gal-
vanized iron. Relate any observations concernir this
practice.',
.-r4
Page-34/0706
C s
Ale
REFERENCES12,
Bosich, JoSeph F. Corrosion Prevention for Practicing
Engineers.' New York: Barnes and Noble, Inc., 1970.
Butler, G. and Ison, H.C.K. Corrosion and its Prevention,
in Waters. NewYork: Reinhold Publishing Corp., 1966.
Higgins, R. A. Materials for.the Engineering Technician.
London: The English Universitiet Press Ltd., 1972.
Metal'Fintfshing Guidebook and Directory,- 47 Annual Edition.
New Jersey: Metals and Plastics Publications, Inc.,
1979.
h
CH-06/Page 35
G OSSARY
Anode: The \po itive electrode in an electrolysis cell.
Cathode: The ne ative electrode in an electrolysis cell.
'Corrosion: The d terioration of a metal because of a reac-tion w-it.h its environment.
\\
Electrochemistry: e field of chemistry ncerned withchemical change\ produced by an electric c rrent, and-the production o electricity by chemical /reactions.
Electrode potential: A measure of the tendency of a metalto go into sorution:
Electrolysis: The process, in which electric current ispassed through a solution of ions to produce desiredchemical reactions. \
\ Electrolytic cells: Device. in which electricity is used,to produce de-sired chemical changes.
Electrolytic refining: A_process in which metals are puri-fied by electroplating them.
Electroplating: A process in which a thin coating of metalis applied to an object, using an electric current.
Galvanizing: A process in whicha thin coating of zinc isapplied to ..an iron, object to prevent it from corroding.
Passivity:- An unusual_inactivity of metals which helps,keepthem from corroding.
.
Voltaic cells: Devices in which chemical reactions are usedto produce electricity.
42 CH-06 /Pagt 37
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I 1 D D
I
O
INTRODUCTION
Approximatelr.three-fourths of the eifrth's elements are
metals. M'any of these metals are important to civiliigtion;
in fact, it is difficult, if not impossible, for people to
go through their daily lives wi0ouvrelyirig upon products'
made from metals: coffee pots, toasters, refrigerators,
automobiles, tools., doorknobs, and countless other items. A
number of important, properties of metals, and\alloys will be
considered in this module.
Ceramics are also studied in this-module. Ceraits and
metals comprise two of the three major materials Wines. 4
The third member of the materiaI*tiamilies, plastics, will
be studied in Module CH-10. Ceramics,have high compression
strength and good "heat and thermal-Shock resistance. Th
ceramics family is large and varied. It includes ceramics,
glass, brick, cement, and porcelain. Uses of these materials\
range from common .tatirelTare-t-o-temperatUre-resi,slapLe-nose--
cones for-rockets.
PREREQUISITES
The student should have completed Modules CH-01 through.
Cg-OS of-Chemistry for Energy Technology I and Module CH-06
of ChemistrYfgr Energy Technology II.
44CH -07 /Page 1
OBJECTIVES
Upon completion of this module, the student should be
able to:
1. Explain the differences between crystdlline and amor-
phous solids.
List some of the advantages of alloys over pure metals.
Match.the types of steel with their chemical composition
or physical properties.
4. ist the three major materials families.
escribe the typeof bonding that occurs 'in metals.
6. ist four members of the ceramics family.
7.' Describe the process making cermets and list some
of their uses..
8. List some of.the,mechanical properties of materials that
are commonly determined through testing.'
9. Define the following terms:
a. Freezing
b. Melting point.
d.xDensity.
e. Specific gravity.
f. Elasticity.
.g. Fatigue limit.
h. Tensile strength.,,
i. Compressive strength.
j. Hardness.
k. Impact strength.
1., Creep:_
m. Ductility.
n. Malleability.
o. Alloy.
p. Cermets.
Page 2/CH-07
SUBJECT MATTER
All metals, except mercury, are solids at room tempera-
ture.' Solids are less compressible than liquids and much
less compresiible th\gases. In fact, solids often are
said to be incompressible. Solids retain their volume and
their origina] shape when placed in a container. At the
molecular.lavelk, the molecules or ions are in rapid motion;
but this ~`motion generally is restricted to vibration.about
a fixed pointt The individual molecules or ions are not
mobile; they /stay in plaCe. These particles arrange them-°./
selves in regular geometric patterns, or lattices not
randomly as is characteristic of liquids or gases.
BONDING
Solids maybe classified into four groups, based on the
type of,bonding that occurs in the crystal: the, ionic
Lattice, the covalent lattice, the molecular lattice, and
'the mexalli:c lattice. An example of the ionic lattice is
sodium chloride. This crystal consists of alternate posi-
tive andnegative ions. TheNhonding, or:force, holding the
crystal together is the attr ctive forces between oppositely
charged,ions: These strong,- attractive forces cause the -
crystals to be hard and brittle with a high melting point. -
Ionic lattice crystals do not conduct an electrical current
when solid, hut will conduct a current when they are, melted.
('In sore solids, the atoms are. bound'together by shared
pairs of electrons to form a covalent molecule. There are
46
CH-07/Page 3
0.
4
no independent molecules in these solids; they are continu-
ous. Diamonds and sand, which are composed of carbon and
silicon dioxide respectively, are examples of covalently
bonded solids.' These solids generally hav2 very high melt-
ing points, are very hard, and are nonconductbrs of electri-
city.
Some solids are composed of independent, covalently
bonded molecules. The -only binding forces between-the mole-
cules are relatively weak polar attractions. These solids
have low malting points, and the crystals, are soft. Dry
ice (which is carbon dioxide) and liquid oxygen are examples
of this 'type of solid.
Solid metals are composed of networks of positive ions
interspersed with clouds of loosely bound'electrons. These
mobile electrons account for the high electrical and thermal
--cuirduct-ivityofme
MELTING POINT'
The temperature at which solid and liquid states can
exist together is known as either.the melting point or the
freezing point, deperlAing upon:the direction of change
occurring. If the amount of solid, in ,equilibrium with the
liquid is increasing, the temperature is referred to as the
freezing point; if the amount of solid.is decreasing,. the
temperature is known as the melting point. Melting-occurs
when the crystal has absorbed enough energy to allow the
particles to overcome the strong fotces holding",them together.
For crystalline solids, this temperature is a very definite
one and may be used to identify unknown sofids4or to check
their purity. Some solids, such as glass and plastics, do
Page 4/CH-07 47
rit
--
not have a regular, geometric lattice pattern. 'These amor-
phous solids can be viewed as supercooled liquids, that is,
they have an.irregular arrangeMent of the particles compris-
ing the solid. Amorphous solids do not have a sharp, fixed,
melting point; rather, they soften and melt over a range of
temperatures;
SUBLIMATION4
or
When heated, certain solids'ire- converted directly to
the gaseous state without passing through the liquid state 5
a process known as sublimation. Dry ice, naphthalene, iodine,
and camphor are solids that undergo sublimation at ordinary
atmospheric pressure. Even solids that can form a liquiyd
phase can subliMe. For example, the vapor pressure of ice
is 4 mm of mercury at 0°C. Even at the freezing temperature
(or below), ice will gradually be converted to water vapor
througl the sublimation process. On a cold, winter day,
even with the temperature below freezing, ice will "disappear"
from streets and trees through the sublimation process.
PROPERTIES OF
. -
Metals have a number of properties that are important
in the selection of a metal for a particular application:
These properties include physical 'properties, such as den-
sity, electrical conclActiirity, th?rmal conductivity, and
luster. The mechanical properties.are strength, hardness,
and ductility. Mechanical properties are determined by 4
48 CH-07/Page 5
application of force. They indicate suitability of a metal
for mechanical service or, use.
DENSII4
Density, defined as "weight per unit volume," is shown
by the following equation:
here:
D = Density.
W = Weight.
D =.Wv
4= Volume.
Density is often measured in terjns o'f.grms per cubic centi-
meter. Density of metals is receiving in'creased attention
because of the many applications and uses 1f metals where c
weight i' an important factor. For.example\ engineers are
constantl Seeking metals Of Irigh strength low weight
fOr use in irplanes and automobiles. In faC,t,-metals are-
berg displa ed by low-de sity plastics in may applications.
S ecifiC ravit is he'weight of a volum of a mate;
0 rial compared ith an equa volume of water. specific
gravity of the ost dense me al, osntium, is app oximaly
40 times that of the,li-ghtest 1, lithium. TIe specific
gravity and strength-to-weight ratios of some metals and
allpys are- given in Table 1. The strength-to-wei ht xatio
is the tensile strength in -pounds per square inch divided
p
Page 6/CH-07.
49 4
by the density. The effect of forming an alloy on the
strength of a metal is clearly shown from the datafor iron
and steel. The strength-to-weight ratio for iron is'in-
creased nearly .10 times by alloying it with other metals to
form steel (from 125,000 to 1,100,000).
TABLE 1. SPECIFIC GRAVITY AND STRENGTH -TO EIGHTIGHTRATIOS OFMETALS AND ALLOYS.
Material .SpecificGravity
. Strength-To-Weight Ratio.(tensile strength/density)
Magnesium ,4
le.ryll,ium alloy..,..
'Aluiinum all(*)?.
Titailiuth-
-
alloy
Steel : '
Iron.
Copper .
Nickel
1.7,
1.& ;
Z.&...
, -4t-E,
7.&
7.9.-
8.9
' &.g
.
.
545,000 4
1,100,000 _____
800:000
1-1-0-0-,-00-0--
'.
"
1,100,000
125,000
. 87,000 ___,;
NN].4.0,000
THERMAL PROP(RTIES
.117-
14.eia1s exhibct,a few.characteristics that are regarded
as their thermal properties: pecif. eat, thermal Con-
ductivity, and thermal expan ion. Specific hea fora given
substance is defined in the metric,ustem as:tithe number of
'calories required to raise the temperature of one gram of
that substance one degree i Generally, metals haire.
50CH-07 /Page
strikingly low specific heats. F r example, gold has a
.specific.heat of 0:032, and lead has a specific heat o
0.034;* whereas, in contrast, w. er has a-specific heat
1.0, and ethyl alcohol.has a's ecific heat of 0.581.
Thermal.conductivity is he rate at which heat Is trans-
mitted through a material. etals usually transfel*heat by
electron transfer and, som= imes, by vibrations of the atoms.
The high thermal conducti ity of metals is due to their. free
electrons, which nonmeta s do not have.
Metals generally i crease in volume when they are
heated. This expansio' usually-is defined as "the change
in length of the meta' when sits temperature is changed one
d grpe." The coeff' ent of expansion of some metals is
nin Table 2, and an example of thermal expansion is
given in example A.
TABLE 2. LINEAR COEFFICIENT OF THERMAL EXPANSION OF METALS.
MaterialLinear Coefficient of Thermal Expansion
(in/in/°F)_
Lead
Magnesium-
Aluminum
Iron.
Titanium
I
0.0000163
- 0.0000151
0.0000133
0.000d065
0.0 047
.
%1/4 I
r.
'Page 8/CH-07
EXAMPLE A: 'THERMAL EXPANSION.
Given:
'Find:
Solution:'
A 100-foot bridge span made of steel (iron
Calculate the increase in length when the
erature increases inwwVIT to, 100 °F. 4
larft x 12 in/ft = 1200 in
1200 in x 0.0000065 in/in/°F x l0pAF
= 0.78 in.
tem-
The 100-foot steel span increased approximately
three-fourths of an inch with a change in temper-.
ature to 100°F. Therefore, it is apparent that
an engineer must consider the thermal 'expansion
of materials-in designing structures that are
Dsubjected to changes in temperature.
/ELECTRICAL CONDUCTIVITY
,-N
Metal atoms haVe valence eleCtrons that are not firmly
associated with one particular,,itom. measure of the ease
with which these electrons/
through, the metal lattice is
vity, wher as the".interference
,e passage of'electrons is' called
electrical resistivity. I/ Increasinl the temperature of a
a '-onar ivity of its ions, there-
ectron flo a decreasing conductiv-
elements o a1met also decreases
a greater mount of imperfec-
wering.
the temperature of
ity: at a temperature near
called electrical conduct'
-Which a-metal offers to
increasesncreases the vib
`may interfering withe
ity. Adding alloyin
condqc.tVity becaus this adds
Lions to the metal lattice.,
metals will increase conduct. /
52Cif-07/Page 9
L.
absolute zero, the metal may become super-conductive. Smee;ectrical devices are kept cold to.increase thgir electrical'
conductivity.
MECHANICAL PROPERTIES AND TESTINGC"\
Strength,hardness,ductility,andtoughness.are mechan-
ical properties of metals. These properties make them useful
in many applications. When metals are compressed or stretched,
the atoms of the crystal are either pushed together or-pulled
part.; .but when the force, or load, causing the deformation
is removed, the metal. returns to its original dimension.
This property is called elasticity. The most common test to
identify the_strength of a metal is to pull a specially con-
Structed'specimen of the metal until it breaks. The value
obtained, called tensile strength, is dependent upon the
orientation and size Of the grains that comprise the metal.
The tensile strength gives the ultimate point at which a
structure would break under a loath' Therefore, in designing
a structure, engineers make certain that the tensile strength
is not approached-closely.
Dynamic, or cyclic, loading is al o a very important
part of the study of the strength of etals. For instance,
aload applied repeatedly can cause racture in a metal at
a much low9' value than'ultimate tensile_ strength. Most
steels have ajaitigue limit of approxiMately 50% of their
tensile strength..
At elevated temperatures, the strength of metals de-,
creases because the activity of the atoms increases and
the-ix attraction decreases. For example, the tensile
4
Page 10/CH-97
4 .53igt
.
,
.. 4
strength of steel is 80W0 psfat ordinary temperatures,
but it is reduced to 30,000 psi at 900°F (482°C.
Compressive strength is the ability of a material to
resist a load that is p1essing downward upon it without
,breaking. High compressive strength is required for founda-
tions, supports, and pillars, suchas those used in bridges.
The hardness_of a metal is a measure of its resistance-.
to indentation or penetration. The three most common haid-4 ,
ness measurement tests are as follows: .Brinell, Vickers, and
Rockwell. The Brinell hardness determination consists of
applying a load of-3000 kg for 30 seconds to a hard steel
ball that is 10, mm in diameter as ,kt rests on the Smooth
suriace.of-the steel to be tested. Then the diameter of the
impressilon-made by- the ball is measured, and the- Brinell num-.
be is calculated. The Vickers test is similar; however, a
diamNiid pyramid is used instead of a ball. In tAe Rockwell
sg.
a
test, the indentation made by a diamondcone under a load,of---4
150 kg is measured. Since the telationship between hardness
and tensile strengthit steel is very consistent, and the.
hardness tests are nondestructive, hardness tests are often
used to give an estimate of.tensile strength. This is a'
convenient Method of checkinvon heat-treatment procedures.
However, (true tensile strength can be detefmine only through
destructive testing.
Impact strength is another important consideration in
material selection. A metal may be strong, as indicated by
a high\teDiale strength, butmay have a low impact strength :
that is, it is relatively brittle. Impact strength, or tough-
ness, of a material.is its capacity for resisting mechanical .
-shock. In'Oetermining impact strength, the test specimen is,
placed where it maAbe struck Wa'heavy pendulum that is
released' from a fixed, height,
.54CH-07/Page 11
a,
4
When stressed over a long period of time, some'metals
extend very gradually, and they may fail at a stress well
below the tensile strength of the metal. This .phenomenon is
known As creep. Such slow extension Is common at high tem-
peratures. The effects of creep must be con.idered in-steam
turbines, boilers, and other equipment subjected to continualhigh,temperatures.
c
Additional metal properties that are important are
ductility and malleability. Ductility is a measure of the
ability of a metal to be drawn into a wire. Malleability
is a measure of the ability of a metal to berolled out orhammered into thin films. .Copper, silver, and gold are
metals that exhibit ahigh degree of ductility and malle-
ability.
The metal tests just considered are called destructive
tests since test pieces are made and tested untiL a failute
. occurs. This type of-test is adequate if the test PieCe -is
representative of the production material. In materials
such as rolled steel anddr,awn rod 7 which are uniform in
properties throughout a large,batch of material fie_struc-
tive testing can accurately predict the properties of a final
produ6t. However, in individually produced parts such as
casti,pgs and weldedjoints the qualiity may vary widely: In
'sucWcases, non-d6structive tests can be used. Non-destruc-
'tive tests,include X-ray methods, gamma-ray methods, ultra-.
sonic testing, magnet'ic particle inspectitn, and dye pene-
trant examinations.
'Page 12/CH-07
yr
,
111
55
4
ALLOYS
An alloy is usually composed of two or more metals; or
it,can'be one metal and a nonmetal, such as carbon, phos-
phorops, or silicon. Althou(gh there are several reasons for
making alloys of metals, the primary one is to improve the
mechanicalibproperties of the principal metal. 'For example,
it. may be desirable to 'increase the hardness, tensile
strength, ductility, or toughness of a metal. Other reasons
for forming an alloy, include the following':
To improve the corrosion resistance of the principal
metal.
To imprcive the casting, hot working, weldability, or
other processing or fabrication characteristics.\\
CLASSIFICATJONS
Alloys can be grouped into three classifications based
upon their structures.
1. The alloy may be a simple mixture in which the component
metals are insoluble in each other and the elements re-
tain their identify. For example, tin and lead (in
plumbers solder) are insoluble in each other in the
solid state.
2. The alloying element'also can be dissolved into the crys-
tal lattice of the major metal to form a solid solution.
3. In intermetallic compounds the atoms of the components
of the ail,loys appear n definite atomic ratio, such as
copper-zinc alloy CusZne:
Cr.
CH-07/Page 13
O
The composition, uses, and properties of some common
elements are given. in Table 3. Some of the alloy.s, such as
stainless steel, may,have variable compositions that is,
' there is a variety of steels that are labeled "stainless.",
TABLE 3. COMMON ALLOYS.
Name Composition Properties Uses
Stainlesssteel
80.6% Pe, 0.4% C18% Cr, 1% Ni -
Resists, corrosion Kitchen fixtures,tableware
Pewter 85% Sn, 6.8% Cu6% Bi, 1.74 Sb
Corrosion resistant Utensils
Dentalamalgam
70% Ag, 25% Pb13% Cu, 2% Hg ,
Easily worked Dental.filling,
Monel 69% Ni, 33% Cu, 7% Fe Resists corrosion,bright surface
Kitchen fixtures
Sterlingsilver
92.54 Ag, 7.5% Cu Bright surface Tableware
Yellow brass 617% Cu, 33% Zn Easily polished,-ductile
'Hardware items
Wood's metal U% Bi, 254 Pb,2.5% Sn, 12.5% Cd
.. .
Melts at 70°C Fuse plugs, auto-matic sprinklers
Silver coins,U.S.
40i- Ag, 10$ Cu --Rosists corrosion-,shiny
Coini--
. .
18 carat,yAllow gold
75% Au, 12.5% Ag,12.5% Cu
Bright, shiny Jewelry.-
&
Nickel, U.S. 75% Cu,i25% Ni 'Corrosion resistant,shiny
.
Nickel coin
Page 14/CH-07 ,
'57
1
TYPES OF STEEL
The most important alloys are those of iron which #e
cald "steels." Iron and steel can be Classified as- fol-
lows: (1) pig iron, (2) 'cast iron, (3) wrought iron, (4)
metal powder-sintered iron,'(5) carbon steel, (6) alloy
steel, (7) high-alloy steel, and (8) tool steel. Each of
these classes are discussed briefly in the following para
graphs.
Pig Iron
Pig iron is not used directly to produce finished
articfes, hut is used as a raw material in producing_more
highly refined iron Or steel. Interestingly, "pig iron"
received its name because it was thought that the rounded
backs of the.bas as they were cast for later remelting
resembled a herd of pigs. \i.g. iron contains 4% carbon;
therefore, it is very hard 4nd brittle. Pig iron is the
product obtained from a blaSt furnace which is _the_ method ,
used to reduce approximately 90% of the ironfore t6' metallic.
,
iron. A blast furnace ,co sists of ti. steel shell _that.
is
approximately 30 feet in diameter, up to 150 feet high, and
>14-nmed with refractory firebrick. Iron Ore (iron oxide), .
(. limestone (calcium carbonate), and coke (carbon) are intro-
. duced through'the top of the furnace. Air that has been
preheated to 1200°F is introduced through the bottom of the
furnace. Thus, the iron oxide is reduced by:theo.carbon to
form pig iron, which is removed from the bottom of'the fur-
nace at intervals. Large quantities Of oxygen are used in
blast furnaces since the addition of about 5% oxygen to the
air yields an additional.W% output of iron.1
, $
'04-07/Page 15 .
58
Cast'Ironti
Cast iron is produced,by heating coke, pig-iron, scrap
steel, and limestone,in A furnace. Although the composition
of cast iron varies, it usually -is high in carbon comment
(approximately 3%). Cast iron is the metal of the foundry;
$.
it is valued because of its good casting-properties, ease of
shaping, and desirable mechanical- and corrosion-resistant
properties.
Wrought Iron r
Although wrought iron is decreasing injopularity, it
still is used in making pipe. Wrought iron/Contists of
approximately .o.or% silicone, 0.02% sulfur, 0.10% phosphorus,.
'0.05% manganese, and 0,03% carbon. Iron, which is the remain,
iig element, makes up the balance.
-Powdered Iron'
Powdered_iron can be converted, into many useful products
of complex shapes.by'the technique called "powder metallurgy."
Powdeted Iron is placed,in a mold and then compacted somewhat.
The article is' then sintered, or heated, near the melting
. point of iron. The sintering occurs in a controlled-atmo-
sphere furnace in order to' revent excessive' oxidation.
Page 16/CH-07. 59
Carbon Steel
.er
The term "carbon steel" is used to denote-those steels
having a carbon content of from 0.005% up to approximately
1.0%. Increasing the carbon content leads to marked in-
t_creases -in hardness and strength of steel. These steels
have specific names, such as mild steel, low-carbon steel,
medium-carbon steel, and high-carbon steel. Carbon steels'
are used to'make the following: railroad rails, springs,
.machine parts, autoframes, and steel for galvanizing and
enameling. Carbon stells may contain small amounts of other
.elements, such as manganele, sulfur, copper, and silicon.
Alloy Steels
It was determined by accident that steels with higher
than normal quantities of alloying elements had markedly
different characteristics than regular carbon steel. The
most commonly-used alloying metals in steel are copper,
vanadium,&nickel, chromium, molybdenum, and manganese. .Since
many alloys can hairetapproximately the same combination
properties,. it is common practice for deigne*-s' or engineers_ cr_
to specify the properties desired of a steel a9d leaVe the
composition up to theproducers. A common use of alloy
steels is in appliCations calling for a high tensile strength
steel, such as in the manufacture of cranes, truck frames,
and railroad cars. This tensile strength is greatly improved
by careful heat-treating of the steel. Alloy steels gener-
allyhave a low concentration of carbon. Steels for use at
elevated temperatures (up to 1100°F) usually contain as much
as 9% chromium. for low temperature a plications, alloy
steels containing as much as 9% nickel are used.
60 61-07/Page 17
.00
.#
High-Alloy Steel
Ithen'the combined amount of chromium, manganese, or
nickel in steel is 10% or higher, the material is called a
"high-alloy" steel. The stainless steels are One major
class of hi:gh-alloy steel. There are more than 30 standard
stainless steels. These are noted for their corrosion re-
sistance, as well as their non-magnetic and outstanding low-
temperature characteristics. 'Unfortunately', stainless steels
may cost 10 times as much as carbon steel. An important
application for high-strength, heat-resisting alloys is in
steam-piping and super-heater'tubing in ahigh-pressUre-
steat, electrical power generating plant. A high'chromium-
nickel alloy is used to withstand the 1100°F operating tem-
peratures in these plants.
k Tool Steel
There is a family of steels manufactured specifically
.for making tools. These toY steels range from carbon steels
"(which are used for their exeeptiOnal hardness) to alloy
steels. Some, tool steels are used in-high-strength struc-
tures, such as airframes of)aircraft.
N
EXAMPLES OF OTHER ALLOYS
. 1 A greater variety of changes can be made in the mechan-
ical properties of iron by alloying with carbon than.by
alloying with any other.element. Carbon can form a true
solution with iron, 9j it may form the compound iron carbide.
Page 18/CH-07
Iron carbide is a' material of extreme hardness that accounts
for much of thp hardening effect of carbon in steel. Manga-
nese genei.elly is added to steel as an alloying element to
combine chemically with the oxygen or sulfur that may be
present. It also prdmotes greater strength by increasing
the hardness of the steel. In high percentages, phosphorus
is detrimental to steels; it causes them to be brittle. How-,
ever, in amounts up toapproximately-4.10%, phosphorus im-
proves strength and machinability of steels. SUlfur and
selenium, in quantities of up to 0.30%; are added to some
steels to improve their machining properties. These elements
.apparently lubricate the tip of the machinini tool, thereby
preventing it from galling dr seizingq
iithsthe material being(
machined. Silicon is used primarily to remove an excess.
amount of oxygen from steel, but it also improves the hard-
ness and strength of the steel. As much as 4% copper may be
added to steel to retard corrosion and increase its hardening
ability. Chromium, the basic element in stainless steels, is
added primarily, for its hardening effect andrrits outstanding
corrosion resistance. An interesting application of nickel
in steel in the manufacture of invar, `Which contains 35-
45% nickel. Invar has an extremely low thermal expansion
characteristic and is used in glassblowing applications wheie
metal-glass seals are required. Molybdenum normally is added
to steels for service At elevated temperdtutes. It greatly
increases the high-temperatur strength and creep-resistance
of alloy steels. Lead is added to many types of steel to
improve their machinability, `thereby allowing parts.to be
machined at greater speeds with consequent savings in costs.
tt
62CH-07/Page 19
CERAMICS
Metals comprise one of the three major materials fami-
lies. The other two, are thR organic plaitics and the ceramic
materials. The inogranic ceramic family is large and varied.
It includes glass, brick, cement, porcelain, and ceramics.
Ceramics, as a class,.have low tensile strengtl and are
relatively brittle. Ceramics haveemuch=highercompressive
'strength than tensile strength. In fact, the widespread use
of cement is attributed primarily to its high compressive
strength. One of the major distinguishing characteristics
of the ceramic family as compared to metals is their
almost totalabsence of ductility. Ceramic materials in
general are considerably'harder than most other materials,
making them especially useful as wear-resistant plrts and
for abrasives and cutting tools.
Ceramics have the highest known melting points of any
materials. Hafnium carbide, for example, has a melting point
slightly abcke 7000°F compared to 2600°f for the metal tung-
sten. Because of-their excellent temperature" resistance,
ceramics are used in linings of furnaces for making glass
"and steel-. --Ceramics. are relatively low_in_thermal_conductiv-
ity and thermal-shock resistance compared to metals.
Almost-all ceramic materials have excellent chemical
. resistance. They are inert to all chemicals except hydro-
fluoric acid. Ceramids have relatively few free electrons
and, therefore, are.nonconductive4 as well as \being good
electrical anthermal insulators.
The Composition of ceramics varies widely. Ceramics 2
contain metals such as aluminum, silicon, magnesium, beryl-
lium, titanium, and boron, cdmbined with non-metals such as.
carbon or_nitrogen. Some ceramics contain only one
Page 20/CH-07
63 .
1
1
I
compound, whereas others contain a combination of two or more
compounds. Alumina (A1203) and magnesia '(MgO) are two of the
most common ceramic compounds that are single compounds.
-, The basic steps in producing ceramic.products are (1)
preparing the ingredients for forming, (2) shaping or form-
ing the part,--(3-).-Ldrying, and (4) firing or sintering.
Ceramics can be formed 1;;-Large number of-'methods in either
the-dry or liquid state. Parts may -be mad-e-- b casting.,
ing, pressing, or extrusion. Drying is conducted-to remove
any moisture prior to firing. DUring firing, chemical reac-
tions occur. These reactions produce the final bonding.
Ceramics have manytechnical uses because of their. high
temperature, and chemical, electrical, and abrasion resistance.
They are used in gas turbines; jet engines, nuclear reactors,
and for high temperature processes. Some widely used ceramics
and their applications are considered in the following para-
graphs.
Refractory, ceramics are prOduced from clays. Alumina
(aluminum\qxide) is the most widely used refractory ceramic.
It is relatively low in cost, is plentiful, and has good me-,
chaniCal properties. Alumina is widely'used as an electrical
insulator and-in appli-cationstutilizing its excellent chem-
ital. resistance. Beryllia (beryllium oxide) is noted for its
high thermal conductivity, which is about 10 times the c31-1-
ductivity'of allWinaand three times the conduct:pity of
steel. Because of, this high thermal conductivity,:combinea
with excellent electrical resistance, beryllia is used for
transisters, resistors, and in other electrical applications
to distribute heat. Unfortunately, beryllia is costly, dif-
ficult to work with, and its dust is toxic, requiring special
handling and precautions. Cordierite is a mixed oxide -used
64 CH-07/Page 21
I 0
in heating ele ents, theT ocouples, radlant4elements in
furnaces, and as furnace refractory brick.4
There are three,co monly used carbides: ilicon carbide,
tungsten carbide, and itanium carbide hese carbides have
the highest melting p ints of all ma erials. Silicon carbide
is commonly known as carborundum; it is used in wear and
abiasion appliCatio s. 'Tungsten carbide is used mainly for
cutting tips-ancit oIs.
Ferrites arm-mixed metal oxide ceramics that contain
high electrical resistivity and strong magnetic properties.
Ferrites are u ed as memory cores for computers; in permanent
magnet motors in automobiles, small-appliances, and portable
electriC too s; and as the phonograph pickup, device.
Glass s an important member of the ceramic familY. It
is one of the oldest and host widely used materials.. Glass
is made rom the most abundant resource on,the earth silica
.or sand. Many types of glass are produced. Soda-lime glass
is th- least'expenive. It is commonly used for bottles,.
kitc enware, windowpanes, and plate glass and accounts for
abo t 90%'of the glass used, in this country. Soda-lime glass
made from soda ash (Na2CO3), lime (Ca0), and high-purity
and (Si02). , Lead -glass is made by utilizing the additives
lead oxide and potash (K2CO3). Lead glass haslecellent
optical prop2ieS and is widely used for lenses in specta-4
Iles and optical instruments: It is also used fox cut glass,'
tableware, and Vases. Lead glass is often-called(crystal,",.-
kthough, like all glasses, it has no crystalline structure.
BorosiliCate glasseshave excellent chemiCal durability,
well a resistance to ,heat_and thermal shock. One variety,
known as r x,-is usedin ovenwite. Another variety, known
as Kovar, can be used, to form glass-,to-metal seals. -.
140 22/CH-07
1
I
1
Borosilicate glasses are used in gauges, sights, piPi g,
electronic tutes, pump impellers, and laboratory gla sfare.
Borosilica e glass contains.approximately 18% bbp65/oxlqd-e../
11. -
Fused qua tz is composed of pure silicon dioxide and is used
in scien ific applications such as prisms, solar-'ell covers ,A
aSers, and radar.
C ramics_generally have high melting poi is and good
g emperature strength; however, trey are -b ittie and
hav poor' resistance to mechanical)hfiock. To "o ercome some
of/the deficiencies of ceramics, tombinations'of metals and
ceramics have been developed. These materials, known' as
ermets, are made by powder metallurgy methods. Powders of
suitable particle size that contain a mixture of metal and.
ceramics are compressed in dies under high pressure. The
powder undergoes a degree of cold-welding and will hold its.
shape when removed from the .die. It is then sintered or
heated to a temperature near the melting point of the metal1
to allot;ti,knitting of the metal particles. Then, the,cermet'
is composed of hard rigid ceramic 'particles bonded in a tough
metallic matrix. The proportion of ceramic-to-metal can'-be
varied to produce cermet' with a range of properties. Cermets
are lises1 i eating elements, bearings, gas-turbine parts,
rocket -en gi and jet-engine parts, lamp filaments, cutins
tools, and grinding tools.
4
f
66 CH-67/Page 23
fr
LABORATORY MATERIALS
Laboratory 1
10 test tubes
Test tube rack /
5 strips of copper, approximately_2 x 1/2 inch
S strips of zinc, approximately 2 x 1/2 inch
Glass rod
L'ead nitrate, -5% solution
Zinc nitrate, 5% solution
Mercurous nitrate, 5% solution
Silver nitrate, 5% solution
Copper nitrate; 5% solution,
Laboratory 2
100 ml beaker
Test tubes, small
HC1, 6 M
AgNO3, 0.1 M
Hg2(NO3)2, 0.1 M
Pb(NO3)2, 0.1 M
Medicine dropper
K2Cr04, 0.1 M
NH401-1, 6 M
HNO3,.6
Unknown Solution containing
or mercury ions
'
Page 24/CH-07
L.,
any combination of silver, lead;
67
rr
)
LABORATORY 1. REACTIO
0 ATORY PROCEDURES
ALS WITH SALT SOLUTIONS.
In this experiment,, strips of zinc akd-cbpper are
reacted with various salt solutions. Equations are to-N
written in the Data Tables for those cases where reactions
occur. Metals are to be arranged in an activity,ser2es.
PROCEDURE
Carefully record all data in Data Table 1.011
1. In separate test tubes, place solutions of copper
nitrate, silver nitrate, mercurous nitrate, zinc ni-t
trate, and lead nitrate.
2. Put a strip ofinc in each test tube. Bird the end'
of ,he strip so that it hangs on the edge o the test
tube.
3. In five additional rest tubes, place solutions of cop
nitrate, silver nitrate;s0ercurous nitrate, zinc:ni-.
trate, and lead nitrate.1 .,'
4. ...Put a strip of copper in each of these test tubes.
, Bend the ,end of the .strip so, that it hangs on the edge
of the test tube.
5:, Let.the.-2metal strips stand in the solutions ',for at
least five minutes. iri
..,
,
6. Remove the zinc strip that has beeri. in the solutionM. ,,...
of mercurous` nitrate.
7. Rinse ,.tfie rub it with a finger: 'Bend the
_____,,sIxip and examine -the broken edge. (1) Whatittetal has
been deposited onthe.strip? Record the ans'I er in Data
Table 1.A
68 -07/Page 25,
4
8. Remove the copper strip' from the solution viith-mercur-t ,
oils nitrate: Rinse and rub with a finger. (2) What
has been deposited on the copper? Record the answer.
(3) What does the color of the solution that reta,ins
inthe test tube indicate? Redord the answer.
Remove the zinc strip from the silver nitrate Solutiop
and remove the deposit. (4) What metal was deposited
on.the.zinc strip?. Record the answer.
,10. Examine 'the zinc strip placed in the copper nitrate
solution. (5)- What was deposited? Record the answer.
lt. Examine 'both of the test tubes in which zinc nitrate-
Was placed. (6) Was there a reaction? Record the.
answer. (7) What occurred? Reco /d a description.
12. Complete the equations inData.Table 1 for those reac-
tions that occurred.
13. Use the data to arrange the metals in an activity series
LABORATORY 2. UAL I ATIVE ALYs OF METALS.
Analytical chem-istry involves'' the methods of.determining
the composition of substances and mixtlares of substances and
solutions. When chemical analysis is restricted to finding
whidh ions are present; the analysis is qualitative. However
when the precise amounts of the ions are determined,,the
analysis is quantitative. Obviously, qualitative Analysis
must precede quantitative, that is, what is present in as
substance qthe composition) must be known before how'Much of
a particular component that is present (the quantity) can be
determined.
Page 26/CH-07
4
69
Ye'
In identifying a u stance such as KC1, one'does not
isolate the potassium in order to recognize this metal. Nor
is chlorine gas obtained from the compound'. This type of
approach would be accurate; but, in many cases, it would be
difficult to carry out, A more convenient and equally
reliable procedure consists of taking the substance into
solution and, by adding appropriate reagents, forming char-
acteristic insoluble compounds of each of the ions: Thus,
in-the case of'KC1, the presence of Cl" would be indicated
by adding AgNO3 to part of the solution. The formation of
a white, curdy precipitate would indicate the presence of
chloride. To another part of the original solution, some
Na3CO(NO2)6 could be added. A yellow precipitate would show .
the presence of potassium ion. A systematic procedure can
be established' to positively identify all of the metals, as
well as all of the non-metals. In this experiment, the
scheme for identifying silver, meycurous, and lead ions is
used. .1x
PRELIMINARY PROCEDURES
Note: The:following procedures contain preliminary
experiments. The purpose of preliminary experiments
is to determine the main reactions of the ions. These.
, reactions are utilized later in the schemes of analyses.
70
I
CH-07/Page 27.
O
Lead Ion
Carefully record all data in Data Table 2.
1. In a small test tube, add two dropi of dilute HC1,to
two drops of the test solution of Pb++
. (1) Note the
nature andscolor of t-he precipitate and record these'
findings in Data Table 2. ,(2) Write the ionic equation
for th.e formation of the precipitate i41 Data Table 2.
2. Allow the precipitate to settle 'in the test tube (or
centrifuge the solution if possible). Decant, or draw
off, the liquid with a medicine dropper. Discard the
solution.
3. Add several drops df water and stir, then remove the
water.
4. To the washed precipitate (from Step 3), add five drops
of water.' Then place the tube in a boiling water bath.
Stir while heating. (3) Does,the precipitate dissolve?
(Silver and mercurous chloride are insoluble in hot
water.) Record the answer.
5. Add one drop of acetic acid and ohe.drop ofK2Cr04'to
the.-solueon. *(4),What.reaciion'is observed.? Recordr
the answer. -
'this, test confirms the presence of lead ion in'a solu-
tion.
t.
f.
Silver Ions.
,1A
Careftilly record all data in Data Table 2.
1. Add two drops of dilute HC1,in a small test tube that),.
contains two drops of the test solution Ae. (5)tNote
r.
Page 28/CH-07
:71
4
the nature and color of theprecipitate and record these
findl1 ingS in Data Table 2. (6) Write the ionic equation
for -the formatiakof the precipitate in-Data Table 2.
2. Allow the precipitate to settle in the test tube -tOr
centrifuge the solution if possible). Decant, or draw
off, the-liquid with a medicine dropper. Discard the
solution.-\
5. , Wash the precipitate by adding two drops of water, stir-
ring; and centrifuging. Discard the washings.
4 Treat the residue of AgC1 with five'drops of dilute
NH3.(NH4OH) an d stir grail the solution takes place. .
5. Add dilute HNO3 - drop-by-drop and stir the mixture'
,aftii-each addition until it is 'acid. To check for the
acid condition, touch the wet stirring rod on dry', blue
litmus paper. if the paper turns red, the solution is
acid. ( 7) What happens? Ruord the answer.-,
MercurouS Ion
Careful record all data in Data Table 2.
1 In a test tube, treat two drops of the test solution of
Hg24" with two drops-of dilute HC1. (8) Note the nature
and color of the_ precipitate and record theIe findings
in Data Table 2. (9) Write the, equation for the forma-
ation of the precipitate in Data Table' 2;
2. Allow the preCipitate to settle in the test tube (or:. _
centrifuge the' solution -if possible). Decant, or draw
off,, the .liquid with a medicine dropper. Discard the
solution.
3. Wash.the residue with two drops of water: Discard'the
washings.
72 CH-07/Page 29NO*
1.
4,. Add two drops of dilute NH3 to the residue and stir the
precipitate. (10)-What is the color of the precipitate? .
Record the answer.
5. Centrifuge and reject the solution.
6. Add aque.regia (one drop of concentrated HNO3, four
drops concentrated HC1) and set.the tube in a water
bath. Heatand stir, until solution is complete.
7. Transfer the solution to a S ml b'ealr and carefully
boil down just to dryness. (Do not allow it to become
completely dry.)
8. Add two drops of vater. Transfer the clear solution to
a test tube and add one drop of reagent SnC12.' (11)
What is Observed? Record the answer.
PROCEDURE
.-
Analysis of SilVer, Lead, and Mercury Ions
Carefully record all data in Data Table 2.
1. Add two drops of dilute HC1 to 1 ml of a test solutibp
containing silver, lead, and mercury ions. .Stir vigor-
ously and allOw the precipitate to settle.
.. .2. Add one more drop of dilute HC1.
3. To the residue, add three drops of dilute HC1 and stir.
Remove the washing's and discard.
4. Add 1 ml of water to the precipitate and place it in
a boiling water bath. .Stir for several minutes.
S. Separate the solution from the residue, transferring
the clear solution to a test tube. The solution, may
be Pb++
,
Page 30/CH-07
,..,
S.
73
I
I a
.
6. Add a drop of acetic acid and five drops of K2CrO4 to
the solution. A yellow precipitate shows the presence
of Pb".
7. The residue may be AgC1, Hg2C12, and same uOiss'olved
PbC12. To remove the PbC12, add 10 drops of water,
set the tube in a boiling water bath, and stir for one
minute. Separate the solution and discard.
8. Add 10 drops of dilute NH3 to the residue. Stir for
several minutes and separate the residue and solution.
9. Transfer the solution to a cle'an test tube. Add another
10 drops of NH3 to the residue and stir. Then combine
the solutions.
10: The solution may contain Ae. Add dilte HNO3 and stir
until the mixture becomes acid. A white precipitate
(or cloudiness) proves the presence of Ae.
11.' If the residue is black, the presence of Hg2" is con-
firmed. However, to ensure confirmation of Hg2+4., add
five drops of aqua regia (four drops Of concentrated HC1
and one drop of concentrated HNO3). Stir; then set in
a water bath and stir until the solutton is complete.
12. Transfer the solution to 4 5 ml -beaker. Then, under
hood, carefully boil this down almost to dryne.ss tck
destroy the excess aqua regia.
13. Add four drops of water and stir. .
14. Transfer the clear °solution to a test tube and add one
or two drops of SnC12. A white, grey,-or black precipi-
tate proves the presence of Hg2++. (12) Obtain an
unknoWm containing Ag+, Pb", and/or Hg2" and analyze
t. Record the answer. in Data Table 2.
40.
74CH-07/Page 31
4
I
DATA TABLES
-
1
DATA TABLE 1. REACTIONS OF METALS WITH SALT SOLUTIONS.
Complete the following equations in the cases where a
reaction occurred:
AgNO3 + Zn
AgNO3 + Cu
Ag2(NO3)2 + Zn
Hg2(NO3)2 + Cu
Pb(NO3)2 + Zn
Pb(N0.3)2 + Cu
Cu(NO3)2 + Zn
Zn(NO3)2 + Cu
Actiirity Series,C
(metal replaced by all others)
I
,
(metal not 'replaced by any other)
t
I
j Page 32/CH-07
a
I
I
I
1
I
DATA TABLE 2. QUALITATIVE A ALYSIS OF METALS.
( 1)
( 2)
( 3)
( 4)
( 5)
( 6)
( 7)
( 8)
{ 9).
'(10)
(11)
(12) Ions present in unknown:-
4REFERENCES
Bachmann, H.G. "The Origin of Ores." Scientific American
20 (June 1960) p. 146.
Cottrell A.H. "The Nature of Metals." Scientific American
218 (September 1967).
Mott, Sir NeVill. "The Solid States." Scientific American
217 (September 1967).
Pascoe, K.J. An Introduction to the Properties of Engineer-
ing Materials. New York: Interscience Publishers, ^,
Inc., 1961.
Rogers, Bruce A. The Nature of Metals. Ames, IA: Iowa
State University Press, 1964.
76 CH-07/Page 33
%
'A
,
111
Tottle, C.R. The Science of Engineering Materials. New
rk
/
York: Chemical Publishing Co., Inc., 1966.III
Starfield, Martin J. and Arthur M. Shrager. Introductory
Materials Science. New, York: McGraw-Hill Book Com-
.. pany, 1972. , .
Van Vlack, L:H. Elements of Material Science. Reading, MA:
R
ill
Addison-Wesley Publishing Co., Inc., 1959.
. .
51:
t
t
..
.Pate 34/CH-07
-
OS
,.
II
GLOSSARY
Alloy: A metal composed of two ormore metals or a metaland a non-metal.
Ceramic: A temperature resistant material composed of a metalsuch as aluminum, silicon, maghesiggi, beryllium,titanium, or boron, combined with a non-metal such asoxygen, carbon, or nitrogen.
Cermet: A material formed from metal and ceramic powders.
Compressive strength: The ability of a material to resista compressive load withogt breaking.
/----Creep: The slow extensioR\of a material.
Density: The weight per unit volume of a material.
Ductility: The ability ofa metal to be drawn into a wire.
Elasticity: The property of a material that allows'it toregain its original dimension after being deformed bya force.
Ferrite: A metal oxide ceramic that has strong magneticproperties.
Freezing point: Temperature at which solid and liquid statesexist together and the proportion of solid is increasing.
Glass: A-member of.the ceramic family that is comprisedprimarily of silicbn dioxide.
Hardness: A measure of a ma1erial'S resistance tortion or penetration.
Impact strength: The capacity of a material for resistingmechanical shock.
Malleability: A measure of the ability of g metal to berolled or hammered into thin films.' 0
Melting point: Temperature at which solid and liquid statesexist together and the proportion of solid is decreasing.
Specific gravity: The weight of a volume .of material com-.
pared w4th an equal volu k of water.
indenta-
78.CH-0/Page 35'
.1
.
4
Sublimation: The direct conversion f a slid into a vaporwithout passing through, the liquid stat
Tensile strength: The strength of a material that is ex-hibited when it is pulled apart.
Page 56/CH-e'1
t
79
at
14,I 4
:A<
, , "? ,
INTRODUCTION
Thermodynamics is the study of the re ationships between
heat energy and other forms of energy call -d wOrk-r/TheAlrin-,
ciples of thermodynamics are important in ower,plailts, _e-
frigeration, and other devices that use,hat to produce power
or-that use engines to add or remove heat. Heat, specific
heat, refrigeration capacity', heats associated with changes
of state, and solar energy storage are some of thee thermos
dynamic topics considered in this module. Heat:transfer,
heat pipes, and heat engines are also discussed.
Thermochemistry is thestudy of the heat that accompanies
- chemical reactions: Calorietry, a method of measuring the
heat effect of fuels, is presented in this module, as well
- as the relationship .between matter and energy. ,1
Thermodynamics and thermochemistry are important to
theenergy technician because they are topics - -that relate.
.1-N\to heat and, therefore, to the fuels that-produce heat.
PREREQUISItES,
The student shouldilave completed Modules CH-01 through
CH-05 of Chemistry for Energy_ Technology I and Modules CH-W .1
and CH-07 of Chemistry for Energy, Technology II.
OBJECTIVES
Upon completion of this module, the student should be
1: Describe the relationshipbetween potential 'energy and
kinetic energy.'
81
61-08/Page 1
2. ,k-Use specific heats to calculate heat gains and losses.
3. Use spezific heats to calculate refrigeration capacity.
4r 1.471qaccihatti the 'mount of heat required for phase*hanges
suckas4usiqn or Vaporization.
5. Calculate the enthalpy (t I heat) involved in the
heating of a substante.
6. 'Discuss the importance of-high specific heat and high
densityfor materials to be used for solar energy storage.
7. Identify three mechanisms of heat transfer.
8. Briefly describe the operation and uses of a -heat pipe.
9. Given the low and high temperatures, calculate the
-d. Energy.*
'Define the following terms:
a
f. Kinetic energy.
g Work.
Calorimetry,
Thermodynamics.
Potential energy. 4 0
m
b. Heat of combustion.
c.
rr
efficiency of a heat engine..
h. Btu. U1. Calorie.
j. Specific heat.,.
I
k. Latent heat......,
1. Heat of fusion.
m. Meat of vaporization.0
n. Sensible heat. -
o. Enthalpy.
p. Superheated vapor.t-
q. Conduction.
r. Convection./I
i
I Page 2 /CH-08
et a
82
,
s. Radiation.
t. .Exo thermic%
U. 'Endothermic.
v. Heat engine.,
A
;
4
.J.
4.
1 I It4
..
a o
.\a
-4.
. 6.
*.0' A
4. atv
4,
..o . .., ft..7
..*: ...a
1 . ::
e
o
e
o
o.
wol 3
; r'CH-08/Page 3:
a.
T, / , .
SUBJECT MATTER
THERMODYNAMICS
Thermodynamics is the science of the relationships be-
tween heat energy (thermo) and other energy forms called
,work ((dynamics) . Because of the energy _crisis, thermody-
namics has gained in popularity, since better utilization
of the energy that is stored in fuels° is needed. Many of1
the principles of thermodynamics are used in refrigeration.
Electrical energy is used to run a compressor that extracts-
heat frbm the air. Thus,, refrigeration is not the mariufac--. e
ture of cold air, but it-is-the removal. of heat. A:refrigera=
tion system is a heafpump, ,that pumps -heat fro a low- tempera-
,
ture level t?.a bigher-temperaure level. From this higher
temperaturetemperature level, the,:heat can- be rejected to air or.
water. .;
An underStanding of heat,:energy, work', and power is impor-,
tart to the' field of refrigeration ands ther'efore, to the,energy technician:
,
Energy is the capgcity to dowork. Energy can be found
0in-many different foims, such as mechaniaq, chemical, elec-
trical, light, or heat. Energy May also be classified, as
e .either.pptentill o,r kinetic :' Potential energyis the energy
th:at'an object possesses tly,yirtue of its position or com:
position Fdr example,wate%i stored beti'rld'a dam has' poten-..
fial energy because of its ,position. A combustible chemical
has potential energy becaUse of'its composition. Kinetic.
,energy is energyof,metidh The magnitude of the kinhtict
emir Aof p object Is given by the following relationship:,..
.!:.,a
4
e
,
2 . t
. . ,
Alt
8
=.1 Ml.r2
.
.* '
C11 -08/Page S
Equation I.:jv
e
a.
where:
k= Kinetic energy.
m = Mass.
v = Velocity..
Thus', the larger, the mass of 4 moving object and the. greater
its speed, the more energy the object possesses. Workis-accomplished 11( en a force moves a.mass across a distance.. . .....f.:
.. 7PthWork is define by the following iWthemarical exprdstion: ',
tiV = f x d Equation
where:
W =.W
f = Force
d = Distana
The,Enilish or engineering unit of work is the foot-pound
(ft-lb). One foot -pound is the amount of worR'resultng
from the movement of an object with a mass of one pound through
).
a distahce of one foot,
EXAMPLE A: CALCULATION OF WORK.
Given: Water.weighs 8.3 lb/gal!*
Find: Amouptof work done in pumping 500 gal of
to.a-height of,100'ft.
Solupro.n: 'W .fxd .
= SOO gal x 8.3 lb/gal x100 ft
= 415,000 ft-lb;
'Page.'6./CH-08
85
water
.
ty
HEAT.
. o:
All matter is-comp iped of atoms and molecules that are, I #
in constant motion. When hea,t,is added to matter; the atom
and molecules increase"i6 motion or vibration Heat is a
form of energy that cannot .1)e teasured directly:' HOweVer,
the intensity of heat can be meas4ed with a thermometer'
lhaI,gives the temperature of a substance. Thierature.is...
a relative value: o-substance is either hot or cold in re-.
lotion to anothe object. For example, boiling water is.
hot compared to ce, but is cold compared to molten iron.
Heat and temperat re should not be confused. Heat is a mea-
sure of a quantit , and temperature i5 a measure of-degree
or intensity Fo example, if both.00ne-gallon and a two:.
gallon container contained boiling water,'the two galls
of water would contain twice as much heat as theone gallon
Of.1yOter, even if,beth had the sdme-temperature of,100°C.
The. British thermal unit' (Btu), is the unit of heat quan-
.tity normally used in refrigeration and other,engineering...r"
work., The 13-tu is 'the. amount of heat energynecessiry to
raise the temperature' of one pound of water ;1 °F. Far example;'
it'takes 10 Btu to raise the temperature of one pound of water
from 85 to 95 °F,./The calorie is th t of heat quantity'used
/
tific work. The calorie s'the heat energy .necessary to/4
.
k rais the temperature of one gromof water_1°C. One Btu
Ni lo s 252 gram ''calories. . /4.
///
CH=08/Eage 7
c
I1
.a
O
s
SPECIFIC HEAT
Specific heat is the amount of heat required to raise
the temperature of one pound of any substance 1°F. Thus,,
the' specific heat of water is one Btu per pound. The specific
heat of some common substances is given in Table 1.
O
'TABLE 1: SPECIFIC HEAT OF 'COMMON MATERIALS.
Material Specific Heat(Btu/lb).
. , .
Aluminum . '0.226BrasS 0.090Copper 0.094Ice . 0.49..Lead ' 0.031Oil' 0.43Steel . 0.11Tin ' v 0.053.Water 1.00Uric 0.096'
ea
In refrigeration work, specific heat is used to deters.
'mine4how much heat must be removed to refrigerate various.-q
producis, such as meat, milk; and bananas. The specific
heats of foods are relatiyely high because'of their moisture.
cvnient.
The amount of heat necessary to change the temperature
of a material,is iiven by :he following eqUation:
Page _8/CH-O8°
°
4
H= W c (t2 -0,041: Equation 3
t87
9,
where:
M = Weight, in lb.
c = Specific heat; in Btu/lb.
-t2 = Second temperature.
t1 = Initial temperature.
EXAMPLE B: SPECIFIC HEAT.
Given: .Five pounds of steel -at 70°F.
Amount of heat required to raise the temperature
to 300°F:
Solution: From Table 1, the specific heat of steel is 6.11.
H. = W c (2 t1)
=. 5 lb x 0.11 Btu/lb (300 70)
= 126 Btu.
In Example B, 1'26 Btu are required to raise the temperatuTe
of iteel4from 70°' to 300°F. -A hotter _object would be re-
Squired to transfer the 126 Btu to.thb Any 1c gain
in one substance is offset by, an, equal heat loss by another
substance. This concept, which is ihe-basis for heat trans-
fer calculations, is illustrated in Example C.
88CH -08 /Page 914
"1
A
EXAMPLE C: HEAT GAIN AND LOSS.
Given: Ten pounds of steel at 400°F dropped into three
gallons glif water at 6,5°F.
Find: Final temperature bf 'steel and water, neglecting
any heat gain or loss by the container walls.
Solution: Heat gain in water, Hw, equals heat.loss in steel
Hs'
Hw '= Ww cw (tf - t1) = Hs = Ws cs (t2 tf).
The final temperature, tf, of the water and steel
will be equal.
3,ga1 x 8.3 lb/gal.x 1 Btu/lb' (t2 66°) =
10 lb x 0.11 Btu/lb (400 - tf)
tf
79°F.
REFRIJdERATION UNITS
.A1 conditioning and refrigeration.equipment is rated
in Btu/hr, in horsepower, and in tons of 'refrigeration.
Chilling to temperatures below freezing requires much more
refrigerdtion capacity than simply cooling air. One ton!
of refrigeration is equivalent Zo the cooling effect of oneo
ton of'ice.pei 24 hpurs. The heat required to melt one !
ton.of ice is 2000.1b (one von) x 144 Btu/lb = .88,000 Btu.
Therefore,'one ton of refrigeration is equivalent to 288.,000,
41,.
Btu/day or 12,000 Btu /hr or 'RIO Btu/min, The relationships
'f'specificheat and Cooling capacity' are given in Example D.
Page ld/CH-08
.1°
89
4,
.
EXAMPLE D: °REFRIGERATIOSI CAPACITY.
One follof beef at 100°F, with a specifiC heat
of 0.77.
F34: Tons of refrigeration required to cool the beef
.to40°F in 24 hours..
H = W c (t2 t1)
= 2000,1b x,0.77 (100° - 40°)
= 92,400 Btu
92,400 Btu 1_Tpns of refrigeration = 288,000 Btu /"ton
n 32
CHANGE6 OF gTATE..
Evaporation and cordensation of liquids were briefly
considered in Module CH-05 of Chemistry for Energy Techol-
ogy X., Matter can exist in three states: solid, liquid,
and gas. Changes from one state to another, such'as evapora-
tion and condensation, require heat Onergy. The heat energy
associated with the physical change in the sta.tqrof a mate-
rial is known as latent heat. The Latin word "latent means
nohidden; -thus, the latent heat is hidden since it causes no
temperature change. For'example, one pound of ice at 32°F
will melt with the additiantif 144 Btu; and the resulting)
water will still have a temper4ure of 32°F. The value
144 Btu /lb 14-44e latent heat of fusion of water.' It is
the amount of.11eat tequire& to melt or freeze one pound of
ice or water ,'at 32°F, The latent heat offusion for different
materials has been determined experimentally and may be
-found in various tables. In the metric. system, the heat
of fusion of war is 80 cal/g.
90 Chi -08 /Page 11
Ip
The quantity of heat absorbed or gilten off if the melt-
ing point of a solid is given by the following equation:
H = W x hL
where:
H= Quantity of heat, in Btu.
W j Weight, ,in lb.
hL
=Eatent heat, in Btu/lb.
The use of this equation is illustrated in Examp e E.
Equation 4
EXAMPLE E: HEAT OF FUSION.
Given: Twenty pounds of ice at 32°F. The heat of fusion
of ice is 144 Btu/lb.
Find: The amount of heat required to melt the ice.
Solution: H = W x hL
= 20 lb x 144 Btu/lb
= 2880 Btu.1
Just as there is a specific quantity'of heat associated
with freezing or Melting., there is also a`lpecific'quantity. .
of heat associated with vaporization or condensation. The
quantity of heat that one pound of a liquid absorbs when
changing into the Vapor state is known as the latent heat -of
vaporization, The word."latent" iscused once again since
Page 12/CH-08
n
I
1
1
1
I
vaporization is a constant temperature process and the heat
is hidden. The heatoof vap ization is found by using th'e
same equation as for heat of usion. The latent heat of
vaporization of is 970 Btu/lb.
.EXAMPLE F: HEAT OF VAPORIZATION
Given: Five. gallons of water at 212°F.
Find:, The amount of heat required to vaporize the
Solution: H = W x hL,
= 5 gal x 8.3 lb/gal x 970 Btu/lb
= 40,255 BtU..
water:
EXAMPLE G: STEAI CONDENSATION.
Giyen:, Ten thousand Btu are remo\sea, from 15 lb 'of steam
at 212 °F.
Finds The amount of steam that will condense into watef.°
Solution: H = W x hL
W = h--
10,000fftiu4 979 Btu/lb
=110.3 lb.,,
Heat has the ability to bring about a change in the.1
physical state of a material (such as freezing or vaporiiation),
1*,
CH-08/Page
0*
Alb
a5 well as the ability to cause a change in temperature.
The heat that brings about a change in state has been defined
as latent heat. Wh heat is absorbed or rejected by a sub- ,
stance; with a change in temperature, the heattr nsferred
is knoim as sensible heat. Thy term "'sensible" used be-
cause the heat cause 'a Chan 'e that can be Sense by the s
sense of.touch, or y a device such as a therthom er.
Total heat the sum of the sensible and th latent
heats of a subs ance.- These meosUrements begin t32°F forwater and -405' fox_ refrigerants in order to avoid- thelarge
numbers obtained if absolute zero is us.ed Total heat is
also known as enthalpy. Calculations used in refrigeration
often involve the use of enthalpy. Enthalpy is-given by
the following- equation:
where:
E =- Enthalpy.
I
E -= W c (t2- t1) +.W hL
W =. Weight of substanOe,, in lb.
c = Specific heat.
ti = Final temperature.
t1 = Initial temperature.
hL
= Latent heat.
Equation 5
The calculation of totaLleat on enthilpy is illustrated1 .
.in Example H.
Page 14 /CH -08
.
e
93C
***
' . ;,
;- "!
2 1
r
'EXAMPLEA-i: CALCULATION:OF ENTHALPY (TOTAL,HEA1;).
Given:
Find:
_Ten pounds of 'ice at 10°F; specific heat of ice,
0.5; specific heat of water, 1.
The total heat requirea to convert the ice to
steam at 212°F.
Solution: First there is a'sensible heat change (H1) from
10°F to' 32 °F, the melting point of ice.
H1 = 10 x 0.5, (32 20) = 110 Btu.
Next,--Ahcrq-is a J-a-tent heat chang,e_LH2) from
ice at 32°F into water' at 32°F.
H2 = 10 x 144 1440 Btu.
Next, th.gre is ar9 sensible heat change (H3) from
.watet at.32° to water at 212°F.
10 x 1 (212 A 32) = 1800 Btu.
Finally, there is a Latent heat ,change (H4) to
convert the water at\212° to steam et 212°F.
HA = 10 x 970 = 9700 Btu.
Hi. +112 + H3. + HyEtotal= 110 + 1440, + 1800 ± 9700
= 13,090 Btu./
.Temperature-enthalpy relationAips for water are shown-4
in Figure 1. This figure shows;graphically what happens
wken one poul;c1,;oi.,..4ge is'heited from 0°F to steam at 400°F.
,Tde first step 'in the process the heating of ice at 0°F" -
'to ice at:32°y. Since the specific heat of ice is g.5-Btu/lb,
it take.s 16 Btu to increase the temperature to 32 degrees,
94
S
CH-08/Page 15
.14'
When 144 morel3tu are added to the ice, it will be converted
to water at 32°F. The latent heat of fusion of ice is 144-
ttu/lb. It takes 180-att)to go frompopit B (32°F) to point
.c
400
350
. 30-
u.250
g 200
150
by 100
tu, 50
0
-0-S0LID WITH TEMPERATURE RISING
SOUD mum..*TO 4LIQUID WITH
TEMP.RISING c
A
/18 Btu
VAPOR WITHTEMP,RISING
UQUID TO VAPOR,
1.44 180 970 Btu--atu Btu T
_
0 88Btu
-200 0 200 #00 600 800' .1000
,ENTHALFty:, Btu/L.1).
Figure 1. Temperature-Enthalpy Relationships for Water..
C (212°F) sine Elie specific heat of water is one,Btu/lb,
and 212 minus 32 is 180. At point C*(212°F) , 'the water --,
vaporizes, requiring the heat of VapOriiation,of w4tes., Which-
is D70 Btu/lb?. .Atcpoint D, all. of the water Chas been,con-.
2 vertpd into isteank. Additional hart causes the tAperature
of.steam to increase. The speciiid heatof steam is 0:47
Btu/lb. ,Therefore, it would require an additional 88 B.1.1
to raise the temperature of the /one pound of steam from 212
tt5 400°F (409 212 =.-.,.188 and 188 .)c 0.47e 8-8). A vapor
such as steam,: which- is above. the vaporization temperature
of the Iiqui,d; iss said to be: superheated. Properties °A
I
4.
Page 16/CH-013 :
95
J(
heatedsteam-and other superheated vapors are found in many
handbooks. The tables indicate'the temperature, pressqre,
volume, and heat content relationships6f the vapors.
r.
SOLARENERGY STORAGE
-°"Solar energy cart only be collected when the sun is
shining. Some of the energy must be stored for use at night .
and during cloudy Rerig0s. The material used for the heat
storage is important to the effic'ient operation of the-,,solar
'system-. T jpridary materials in current use are water,
stone, and concrete. The specific heat'of a material is.
An important consideration.in its use as a solar energy. storage
_ medium. Some of the important pr erties of materials used
for storage dre given in.Table As can be seen in Table
dater is-,the most effecti heat storage matetial. Water
has.the capacity to, store nearly twice as much. heat per cubic.
*L.
Vt-TABLE 2. PRCARTHS.OF 'COMMON SOLAR .STORAGE MATERIALS.
.
Material,Specific Heat
(Btu/lb)Density(lb/ft')
Heat Capacity.(Btu/ft')
.Water ''Stone -,:\
Concrete
, 10,21
0:21.'
4
, 62.5
180140.
/
/
. , - 1
62:5 .
.36
38
a
foot as:stone.or concrete.' ,High speoff'c heataf,:high den-
sity are desirable for heat° storage. Certain_ salts th4t .
li
'96°At
- CH-08/Page17,.o
ty"
r.
4
store heat by melting rather than by getting hotter are being
developed. ,These materials store hat'of fusion at a con-
stant temperatTe, Experimental development of these,mate-
riali. 11(1 Other that rely upon heat'o4, reaction (such as
the heat of reaction between sulfuric acid and water) isP
und7ay.
HEAT TRANSFER
I
Heat, always flows from a warmer - object to a colder ob-
ject. The rate of heat flow depends on t.h.temperaiure4
ference between the two objects. The transfer of"heat from
one'plage'to another occurs in three ways:" (1) conduction,
(2) convection, and (3) radiation. Conduction i$ the flow
.`of 'heat thrOUgh an obiject./-F6,n conductive heat transfen. .
betweentwO objects,' they must be in:contact. ,Some. materials,
' such as Meta;1, conduct heat readily.; others, ,such as 'glass,.
wood, and cork, do not conduct heat 'readily. These non-
conductors of heat are called insulators. ,,Convection is.
the flow- of heat by the .use of a fluid, either gas or\litluid..
The convectivefluids most often used for conVectiVheat 4ransfer ar%
ai'r and water. A heat ed fruid*is les's dense and" rises,
whereas a cool fluid is more dense and'falls. This causes
, a continuous movement. of the luid, giving risen to natural
convection:: If.the fluid currents are caused bj, a. pump orfan, the term "forced"convectiOn" is used. RA:nation is
the transfer of heat by wave motion:. The waves may be light
wavekor radio 'frequency waves. 'The .beat telt in front of
a fir;i3lac or in direct sunlight is an example of radiant
heating. The air between the objects is notheated, just
the object itself.
Page'18/CH-08 4
HEAT PIPE '
AS. indicated above, the rate of heat tra4sfer,by con-. . .
duction is proportional to tfie difference in temperature.
of the two- objects: A relatively .new (19'64) device has been
developed,00r fftnsmitting heat at a 'high rate over a con-
.siderable-distance and with an extremely small temperature.
drop. The nat pipe ivespecialljr attractive since it re-.
quires no external pumping power. The heatopipe is a cloSed
tube with inner surfaces that are lined with- a porous capil-, 4
'lary wick. The wick is saturated with the liquid phase of
a fluid, and the remaining volume of .the tube contains the
vapor phase of the fluid. Heat applied at one end (the
evaporator end) by an external heat source vaporizes the
fluid in that section of the pipe. The resulting difference
in pressure drives vapor from 'the evaporator to the condenser
end of the pipe where it condenses and releases the latent
heat of vaporization to a heat sink in that section of the
pipe. Depletion of the liquid by evaporation in the evapora-
tor: en-a of 'the pipe causes liquid to enter into the wick
surface. Then, capillary,pressure'pumps the .condensed liquid,
back to the evaporator for'revaporization. Thus, the heat
pipe indefinitely transports the latent heat of vaporization
from the evaporator to the condenser. The amount of heat
that can be transported as latent heat of vaporization is
usually.several, orders of magnitude larger than that which
can be transported as sensible heat in a conventional con- ,
vective system. The heat pipe'can transport a large amount
of heat with a small pipe-size and a small temperature dif-
ferential. Heat pipes.have.been developed which are mofe
ective than the most conductive metals. Heat pipes are
used to recover heat from the exhausts of industrial boilers, '
itp.
98CH-08 /Page:19
" furnaces, and kilns. Heat pipes are also used for heat
recovery from HVAC (heating, ventilation, air conditioning).
systems.
HEAT ENGINES.
A
The basic principle of a heat engine is illustrated .in
Figure' 2. A certaidamount of heat, qh, is absorbed by the
working fluid of the engine,HIGH TEMPERATURE. Th
LOW TEMPERATURE,
Figure 2.Heat Engine.
at a high'temperature, Th.
The heat is partly converted
to work; w, and the remainder
'of the heat, q1, is rejected
to the surroundings at a lower
temperature,'Tl. the tempera-. .
tures must be expressed on
the absolute (Kelvin) scale.
The efficiency of'the heat
engine, an important value,
is given by the following equa-
tion:
F Th TiEfficiency Equation 6
If the two tempe'ratures, inlet temperature and outlet tempera-.
ture, are the same, the efficighcy of the heat engine is
zero. A steam engine_ operating between 100°C (the boiler
tethperiture) and 25°C (the condenser temperature) would have
0
Page 20/CH-08
99
' I
an efficiency as calculate&below:
-Efficiency
373 298 -.0.20
The efficiency of this engine is 2ply 20%. The waste
heat is 80%, a tremendous loss in heat. To imprOve effi-
diency, modern power plants operate under high pressure,
using superheated steam. NeVertheless, most power plants
operate at less than 40% efficiency. Thus,, more than half
of the heat is wasted.
THERMOCHEMISTRY
Thermochemistty is concerned with the heat that accom-
paniei chemical reactions. .Thermochemical eguations indicate
the state of the materials. Solids, liquids, and gases.ai-e
de4ignated by (s), and (g), respectively. For the com-
bustion of carbon the following reaction is,u$ed.:
.
C(s) 02(g) CO2 ('g) = -94,062'cal/mole
This r indicates that solid carbon,burns'in gaseous,
oxyg orm gaseous carbon dioxide. The AHis the heat =..
of r tion, or enthalprchange.% The.negative sign indicates
that hea is evolved in the burning of carbon,.... Most chemical:,
reac ions give off heat and have a negative enthalpy: These
reactions are exothetMic 'reactions. '.Those reactions in which
)
166cf1-08/,Pade
4
9
hea't is absorbed are endothermic reactions. They have" a
positive enthalpy-change.
In most.combustion'y exothermic reactions, the products
are of secondary importance. What is more important than
the products is the energy being produced. In contrast,
most endothermic reactions are conducted because the products
are of primary importance that is, energy is utilized to
form useful products;
RELATIONSHIP BETWEEN MATTERANDf ENERGY
Energy may be transformed,or changed from one type to
another. Chemical energy may be converted to heat energy,
heat energy to electrical energy,'mechanical energy to elec-.
trical, and so forth. However, in none of these changes
is there a change in the total amount of energy that is,
the sari of all forms of energy remains constant. The law
of conservation of energy states the following: Energy cannot4
be created or destroyed, although it can be.changed in form.
Likewise the law of conservation of matter states that there.
is no change in the quantity of tatter during an ordinary
chemical change. This law is-,the basis for all analytical
calculations and determinations.
These two laws concerning conservation of energy and
conservation of matter are only applic'able for ordinary chem-..
ical reactions. In 4905, Albert Einstein first proposed.
the relationship between matter and energy. This relation- :
ship, usuaaly referred to as EinsteindS Equation; is fol.-
lows: 4
. .Page 22/CH-08 101.
E ,= mc2
AT.
E4Vation 7
where:
-E-,En,ergy of a reaction.
in = Mass being changed to energy.
e = A constant, the speed of light.
This relationship between tatter and energy is significant
only in nuclear reactions. -The laws of conservation of energy
and matter may be combined and stated as follows: Matter
and energyca be neither:created nor destroyed, but they
can be transf8rmed, one to the other.
CALORIMETRY A
Measurement of heat effects of chemiCal and physical
changes is Cl.led calorimetry. One of the most' common calori-
metric measurements is the heat pf combustion ,of materials.
Fuels, such as coal, gasoline, ottl, and gas, vary in the
amount of'heat that 'different samples of each will produce.
When buying.fuels fuch as coal, it is important to know the
amount,of heat that a given fuel will produce.' The price
of coal-and other fuels depends upon ,their grade, which Is
assigned by a calorimetric measurement.,
The Neat evolved in the complete oxidation of a substance
is knowh as the heat of combOtion. Heats of combustion
of various.sUbstances are given in Table 3. The values are
in kcal per.gram of substance,burned to H2O and c02 at con-
stant pressure and 25°C. In.the English system, heats of
combustion are'reported in units of Btu/lb,
Oe 102 CH-08/Page123
4
ti
p
TABLE '3. HEATS OF COMBUSTION.
Sub'stance
i
Heat of Combustion(kcal/g)
.
Hydrogen.
Carbon
Carbon monoxide
Methane
Propane
Octane
Acetylene
.
,
-33.9
- 7.8
-,2.4
-13.3
-12.0
-11.4
-11.9
.
,
4t,
,Heats of.combustion are measured in a bomb calorimeter.
A schematic of a bomb calorimeter is shown in Tiguie 3.
+ - ELECTRICAL LEADSFOR IGNMNG SAMPLE
a
Figure 3.INSULATED CONTAINER Bomb Calofimeter.
BOMB(REACTION CHAMBER)
FINE WIRE IN CONTACTWITH SAMPLE
CUP HOLDING SAMPLE
WATER
Page 24/CH-08
1.63
Q
f
t'
a
To'deterMine the heat of combustion in a bomb calorim-
eter, the ,following procedure is ute. .Thesample (usually
1 g) is weighedvand mounted on a holder inside a thick,
stainless steel bomb. Thke bomb is sealed, and oxygen gas
is added through a valve to a pressure of 25 atmospheres.
In an atmosphere with this elevated amount of oxygen con-b
centration, complete combustion of most fuels is assured..
The sealed bomb is placed in a container, and exactly 2000 g
of water is added 'to the container. This container is then
placed inside an insulating container. Avthermometer and
a stirrer are placed in the water surrounding the immersed
bomb. The water is stirred at a constant'rate tintil.tempera
ture equilibrium is attained. Then the sample inside the
bomb is electrically ignited. The rise in temperature: is
measured carefully and can'be used to calculate the heat'
of combustion of the sample.
To standardize the apparatus, the caloritheter constant
must be obtained. A known weight df a standard, such as'a
very pure benzoic acid, is comnsted. From the known amount
of heat absorbed by the lkalorimeter, and'the measured rise
in temperature of the water, a calorimeter constant is cal-
culated, using the following equaltion:,t
Calorimeter 'Known heat of combustionconstant Measured change in temperature
Equation, 8 -
I.
The heat of combustion of'a unknown 'substance can be deter-
mined bihurning a comparable weight of a sample and multiply-.
ing.the rise in temperature by the calorimeter constant.
104
sif-N7
CH-08/age 25
;
)
e
Since man/ fuels contalnnitrogen and sulfur.,-a correction
must'be made'to obtain the true heat of combustion. 'Usually
1 ml of water is placed in the bomb prior tb'..c.bmbustion in
order to absorb the sulfur oxides and nitrogen oxides formed.
The reaction with water forms acids that are t'itrated with
standard sodium hydroxide to obtain a measure of the amounto
of sulfur of nitrogen impurity in the sample..
F
Page 26/CH-08
I
105V
4
'c
LAI3ORA1" ORY MATERIALS
Lgboratoryl.
Calorimeter (two poly-styrene "coffee" cups,cardboard cover)
Thermometer
Lead slot.
4 Iron shot,
Clock or watch with secondhand
600 ml beaker
Burner
Balance
Test tube
Laboratory
C4loriteter (sameas Lab, 1)
Thermometer
J(C1
,1.0 M NaOH
h.6 M HC1
Magnesium ribbon
Sandpaper
LABORATORY PROCEDURES
LABORAsTORY 1. SPECIFIC HEAOF A SOLID ELEMENT.
Procedure
Record all data in Data Table 1.
,I. Assemble the.calprimeter, as shown in Figure 4
2. Put about 300 ml of water into a 600 ml be'aker and_ hea.t
to boiling.
3: Measure the temperature and record as Tb.
4. Uting a triple-Veam or fop-loading,balance, weigh
100 g of le4d ot 'into a test tube.
5. ,Place the test tube in the boiling water and allow the
tube to remain in the boiling water for five minutes.
(Tie lead should now be at temperature Tb.)
106 'CH-08/Page 27
Nt,
.
\
o.
THERMOMETER
K
CARdEOARD COVER
POLYSTYRENE CLIPS,
Figure 4. .Calorimeter.
r
6. Pfur 100 ml of water into the inner cup of the caforim-,
eter.'
7. Measure -the temperature of tIn calorimeter water and
record.
8. Remove the testtube-from the heating bath and'oluickly
pour, the lead. shot into the calorimeter water and .cover
with the cardboard top. ,
9. Stir for 30 seeOnds' and record the maximum tempeOturd
as.Tf.
ib. Repeat the procedure,:,using,iron shot.
The, amount 'of heat absorbed brthe.calorime/ter is giveh
e)y the following equation: :
Heat absorbed = Trf x 100 g x 1 ,cal /g - °C
Page 28/CH -0$
.1
9
,
1.
1
"The heat absorbed is equal to the heat added from the
hot lead or iron./Specific heat
Heat'delivered = 100 g x (Tb Tf) x of metal
Equating the' two equations,
100 g x (TbTf) f
Specific heatof metal =,(Tf Ti) x 1. %.
. , . ..,
Solving for specific heat,
(Tf Ti) ))c 100 g x 1 cal/g=°CSpecifdc heat
4 100 g x (Tb Tf)
11. Using this euationo'calculate the specific heats of
lead and iron and compare the values of those fdund
in a handbook.
LABORATORY 2. HEATS OF REACTION.
Or
fChemical and physicar changes are usually accompanied
by the liberation or absorption.ol. heat. When a salt is
--dissolved in water,. the resulting solution may be either
warmer or colder than the.water was. 'The heat of solution
of a substance is the heat change when, one mole of the sub-
,stance is dissolved in a largeambunt of solvent. The heat'
of solution, DH, of potassium chloride will be determined
in this experiment.,
When a strong acid'ind a strong base are' mixed, a con-
sIderable quantity of heit is given off. In this experiment,
the heat, that r5 liberated when hydrochloric acid and sodium
108CH-08/Page 29
hydroxide areimixed is determined. This qua y is called
the heat of solution.
Finally, magnesium metal is dissolved in` hydrochloric
,acid and the heat of reaction is. measured.
PROCEDURE
Heat of Solution'
Record all data in Data Table 2. a
1. Assemble the caloimeter, as shown in,Figuret.
2. Measure 75 ml of water with a'grauated cylinider and
transfer the water to the inner polystyrene cup of the
calorimeter.
3. Accurately weigh a quantity of potassium chloride be-,
tween 1.5 and 2.5 g. Record.
'4. Measure the initial temperature of the water. Record-.
5. Add the weighed amount of KC1,to the water and swirl
the cup gently to dissolve the salt. Observe the
temperature and, when it is constant, record the value.
6. Calculate t e number of calories involved in the re-
action. 1 of water weighs 1 g. Pocalorie is the
amount of Feat required- to -raise the temperature of
1 g of- water. 1 degree C.) Record.
7. Calculate the number of moles of KC1 which were dis:
solved. Record..
8. Calculate how many calories would be involVed if one
mole of KC1 were dissolved in water. '(This is the heat
of soltAtion.). Record.
,Page 30/CH-08--TOO
Heat of Neuttalization
Record all. data in Data Table 2.
1. Measure'50 M HC1 with a graduated cylinder'ind
transfer it to the inner cup of thecalorinver.
2. Measure the temperature of the HC1 in the cal6rimeter.
Record.
Measu 50 ml of r M NaOH with a graduated cyliiider and
'add it to the HC1 in the cup.
4. Mix the HC1 and NaOH and recoryl :temperature when it
.becomes constant:
5.. Calculate the number of calories involved in the reaction..
Record.
6. Calculate the number of moles of HC1 that were neutralized.
Record.
7. Calculate the number of calories,which would rbe involved
if one mole of HC1 were neutralized.' (This is'the heat
of neutralization.) Record.
t.
Heat of Reaction
'Record all data in Data Table 2.
1.. Clean a piece of magnesium ribbon (weighing about 0.1 g)S
with sandpaper, and then weigh the metal accurately.
2. Add 75 ml of ,1 M HC1 to the inner cup of the calorimeter.
IP 3. Record the temperature of the acid.
4. Place-the'magnesium.ribbon in the acid and swirl-the cup.
5. Record the temperature when it'becomes constant.
.6- Calculate the number c)..calories of heat given off in the
reaction. Record.
CH -08 /Page 31
4
7.
10
Calculate the number'of moles of magnesium used. Record.
. Calculate the heat of reaction that would have been
observed if one mole-of magnesium had been dissolved.
9. The accepted value for the heat of this reaction is
110 kcal/mole. Calculate the percent'difference be-
tween the accepted and the observed values. Record.
DAT44 TABLES-
DATA TABLE 1. SPECIFIC HEAT OF A SOLID ELEMENT.
Step Procedure ' Lead. AN
Iron
3.
7.
1 9.
li.
Temperature, Tb
Temperature.of water, Ti
MaximUm temperature, Tf
Calculated value of specific heat
Handbook,value of specific heat
.
. .
,
page 32/CH-08
rr 1,
,1
L.
DATA TABLE 2. HEATS OF REACTION:
Heat of Solution:
Step
3. Weight of KC1
4. Initial temperature of water
5. Final temperature of water
6. Number of calories liberated
7. NUMber of"moles of KC1 used
8. Heat-Of solution (cal/mole)
Heat of Neutralization:
Step
2. Temperature of HC1
4. Final temperature of HC1-NaOH mixture
5. ,Number of calories liberated
6. Number of.moles of HC1 used
7. Meat of neutralization (cal/mole)
,Heat of Reaction:
Step
1. weight of-Mg, ribbon:,
3. Temperature of acid
5. Final.temperature of mixture
`6. Number oCcalories of heat given off
7. . Number of molesof Mg used.
8. Heat of reactig,mesal/mole)
9: % difference between a9,cepted andexperimental values
*a'
.112'CH708/Page,33
0-*'
c
REFERENCES ---,T-4
(-Babit's, George F. Applied Thermodynamics. Boston: Allyn
and Bacon, Inc., 1968.
Chi,S.W: Heat Pipe Theory and Practice. Washington:
"Hemisphere Publishing Corporation, 1976.
Davies, Clive. Calculations in Furnace Technology. London:
Pergamon Press, 1966.
riEmswiler, J.E. and Schwarts, F.L. Thermodynatics. New York:
, McGiaw-Hill Book Company, Inc., 1943.
Strauss,` Howard J. Handbook for Chemical Technicians.
New Yo'rk: McGraw-Hill Book Company, Inc., 1976.
Page 34/CH-D8
1
a
GLOSS/TY
4
Btu: The amount of heat necessary to raise the temperatureof one pound of water 1°F.
Calorie: The amount of heat necessary to raise the tempera-ture of one pound of water 1°C. .
Calorimetry: The measurement of heat effects in chemicalreactions.
Conduction: The flow of heat through an object.
, Convection: The flow of heat by use of a fluid.
Endothermic: Absorbs h
Energy: The capacity tg1do work.
Enthalpy: The total heat of a substance.
Exothermic:. Gives off heat.
Heat engine: A system thaf relies upvn differences intemperature at the inlet and outlet.
Heat of combustion: The heat evolve in the complete oxida-tion of a substance.
Heat of fusion:, The amount of heat required to melt a sub -.
1
. Heat of vaporization: The amount of heat required to vaporizea substance,:
Heat pipe: A device for tra Eerring, heat that does notrequire a large in inlet and outlet tempera-
, tures.
A Kinetic energy: Energy due to- motion ,of an object.
Latent heat: The heat associated with a change of stateof amaterialat 'constant temperature.
energy The energy that an object,has by virtue. of its position or composition.
114 CH-08/Page 35
fi
"ty
r
Radiation: The transfer of heat by Wave motion.
Sensible heat: Heat'absorbed or rejected by a substance,with a change in temperature.
Specific heat: The amount of heat required to raise the )temperature of one pound of 'any substance 1°F.
Superheated: A vapor that is above its vaporization-,I0eera-turer
Thermochemistry: Trke branch of chemistry concerned with theheat that accompanies chemical reactions.
Thermodynamics: The study of the relationships between heatenergy and other forms of work.
0
Total heat: The sum of the sensible and the latent heats .
of a substance (also known as enthalpy).
Page 36/CH-08
O
4'.
INTRODUCTION
The energcrisis is posib4 the 'greatest problem fac-
ing society. In the, United Stites, the use 6f energy is in-
creasing, whereas the availability of enertLil decreasing.
Energy consumption has been increasing at the rate of approx-
imAtely3.5% over'the last few years. This energy is cur=
rently,. being supplied by petroleum, Coal, natural gas', water
power, and nuclear power -7
Energy use, has increased'as society has become'less agri-
cultural and more industriaized. . recently As the 1940s,
more th'an three-fourths of the world's population was at a
primitive agricultural, level', requiring relatively little
energy,. 'Today, one-third ,of the world's population lives
)in,-an indUstrialized society, corituming 80.%lof the world's
energy production. The UniAd States, with '6% of the world's
population, uses one-third of the yearly'energy.production.
As more and mgre of the pOpUlace become significant energy ,N
users; the competition for energy will become very severe.
'Moss of the energy production ;throughout the world de-
pends upon fossil fules: Coal, petroleum, and natural gas.
These -fuels were formed millions oLyeais ago from buried:
plant materialc, These. fuels are not replaceable; therefore,
alternate, fuels must be0oughe'as the fossil fuels arede-.
.
pketed. The fossil fuels., in addition to being used for. .
'are"used as the raid material to, produce chemicals.
This 'secondary use compounds the,shoitage_91-fuels and makes,,4
it vital that alternate energy sources be developed.
ALT
117CH -09 /Page 1
.1
. Aii, ,
"--1, ..
:PREREQUISITES :. .
I& ,. , , ,.. .. .
e-,
The student, should cwletedModules CH-01-through
CH-05 of Chemistry fow _Energy .Technol9gy I and Modules CH -06, II
.,_
CH-07, and CH-08 of Chemistry for Energy Technology II. s
014',IECTIVES ,.,
* ".
.
Upon completion of1thT4
module, the student should.
.r 11be able to: .,
1 Define the following ,,:terms.t
a., Petroelum., 7 I. ,
b.' Octane umbef:
c. Cracking.
d. Antiknock agent.
e. Refining. 1f. Polymerization.1
II
g. Hydrocarbon.. ,:
h. Isomer.
i. Alkane.
j. Alkene e , II
k. Alkyne.
1. Aromatic hydrocarbon,'II
2. LiSt the characteristics'of a go9d fueT. 4
3.'. 464Vmpart the coMposition,,properties', and' fuel values -, .
JPof anthracite, bituminous., and lignite coal. .1,
4. Identify the major constituents of-gasoline.'
5. Write the chemical'reactions for the combustion Of Ifue% .
i. ls
6.4., List the major fractions obtained in petroleum refining-
7. List and explairithe purposes of theprocessesiused
to increase the yield oy gasoline. .
Page 2/CH-09
ter' y
.s
LIE?
8. IdentifYseveral nonconventional or alternate en.ergy
sources..
9. Liset the geneial differences between organic and in-
organiC compounds,4
10. Name two factors that account: for the large numberA
of organic compounds.
List'the names of th'.first eight/members of the alkane
series of hydrkcarbons.
12. Match the formula of an organic radical with its name.
13: iletntify functional groups in the major classes of
substituted hydrocarbons., . '
7
r
.CH-69./Pag0 3
i,
0
SUBJECT MATTER
CHARACTERISTICS OF FUELS°
A fuel is ahy cotbuStibe,substande thSt is burned to
produce usefulheatenergy. Fossil fuels were and'are
produced by the sun's energy in the photosynthesis of grow- N..
ing plants. These fuels include wood, coal, oil, and natu-
ral gas. To meet the demand for enegy, :more direct ways of
utilizing solar energy must be developed.
There are a number of desirable characteristics in
fuels. A fuel should produce a large amount of heat energy
in proportion to its weight. Fuel's must be low in cost and
available in large quantities. They must not prodtice combus-
tion products that are dangerous, and they should not leave
large'amounts "of residue after combustion. Finally, it is
important that fuels can be easily producedwvhandled, and
transported. Oil and natural gas are the closest to having
all of these desirable characteristics andtherefore, are
''the most popular fuels.. They are easily transported, are
fairly inexpensive, and leave virtually no residue after,
The heat con'tent,of coal, petroleum, and natural gas is
given in Table 1. As shown, natural gas has a relatively
high heat content; it contains 70% more heat than
coal .4
' ,
120
t
CH,09/Page 5
; I
4
TABLE 1. HEAT CONTENT OF FOSSIL FUELSAND USAGE IN THP UNITED STATES.
--
Fuel
, Heat Content(keal/gram'of fuel) Usage
Coal
Petroleum
Natdral gas
'----
7.8
11.4
13.2
.
21%.
45%
34%.
..
SOLID FUELS
es
Historically, wood haS been the most important fuel,0
although its current use as a fuel is rather limited. Most
of the World's production of wood is used in the construc-
tion industry, in the manufacture of paper and textiles, and
in the production .of a variety of products through des4ic-.
tive distillation. The destructive distillation of wood pro-
duces wood alcohol (methyl. alcohol), acetic acid, acetor1e,
creosote, wood tar, charcoal, and several combustible gases.
There'are several important forms of coal. Anthracite,
or "hard" coal, contains about 80% carbon;,,whereas bituminous,
or "soft" coal, cOntains'about 60% carbon. In spite 'of the
lower carbon content, bituminous coal has a higher heat value
than does anthracite, because the bituminous coal contains a
considerable amount of'volegiile hydrocarbons that have high
heat value. Anthracite burns with a clear flarde that pro-
duces little spot. Lignite contains even less carbon than
bituminous coal. This brown coal exhibits much of the str.uc-.
ture of the wood from which it was derived. LignIte is found
Page 6 /CH -049
121
h
---in veins near the suriaeeandisstrip mined. Peat is com-
pressed moss that has undergone some of. the processes that
formed coal. ,
Coal is the most abundant' ssil fuel'It was estimated
that, at present'consuMption rate \coal could last for up.
to 500'years. Unfortunately, the rate of consumption is in-
creasing 3.5% each year. Two of coal's major drawbacks are
that it is a relatively dirty fuel and it is difficult to
handle. The atmOsphericollution caused by coal, especially'
txlfur- containing coal, is severe. In addition, deep coal
mining is dangerous and unhealthy to miners; and stripaining -. -
can have a serious ecological-impact.
In spite of the severe problems connected with coal
must supply the majen-tenergy needs for the next decades. t..6Qal
can be used directly to produce heat upon combustion, as
it
,
.
C + 02 + 94 kcal/mole
I
Extensive research and development efforts are being made to
convert coal to gias or liquidprior to its-use. Coal gasifi-
cation can be used to convert coal into a relatively clean
burning fuel. I:this process, coal is reacted with hot air
or steam. The reaction with hot air produces a gaseous mix-
ture called power gas; which contains as much as 50% nitrogen:,
Since nitrogen does not burn', power gas hac,a very low, heat--
,ing value. The reaction is as follows:
CH-09/Page 7
4Or-
..
C + CO + H2 N2
Coal (Power gas)
If the coal is reacted with steam, emixture of carbon mon-
oxide and hydrogen, known as coal gas; is obtained:
C + H20 CO + H2
Coal Steam (Coal gas)
The carbon monoxide and hydrogen from either power gas or
coal gas will -burn to produce heat:
2 H2 + 02 2 H2O + Heat
2 CO + 02 -D- 2 C + Heat
Coal can also be reacted with hydrogen to produce methane by
the following reaction:40
C+ 2 CH4
Coal Hydrogen Methane
The methane can then be burned. This process is not fully ,
developed, but it is promising since the coal -can be burned
in'a centr41 processing plank And the methane then piped'
Page/I/CH-09
123
inexpensively, through the existing atural gas lines to the
customer. Liquid fuels can also .e made m coal by several
liquification processes. Liquiv fuels rom oal can possibly,
be used as a substitute for gas in-. Since coal is pre--
dominately carbon, additional hydrogen is aided to'form
petroleumlike hydrocarbons. The hydrogenatioi of coal must
take place at high temperatures and pressUres thus making
the process a difficult challenge. The most promising meth-.
ods operate on the principle o.f contacting crushed coal, with
selective solvents that act as hydrogen donors to aidlin con-,
verting it to a liquid phase. Final hydrogenation is then
conducted in the presence of a catalyst.
GASEOUS FUELS
Generally, gaseous fuels are relatively easy to trans-(
port; and they burn cleanly. As indicated previously-, coal
can be reacted with steam ,to prodUce coal gas. One tOri of
bituminous-coal can produce as inuch as 12,000 cubic feet,of
coal gas, as well as 1200 Tounds.of coke, 120 pounds of coal
tar, and ammonia. The coal tar is rich in valuable aromatic
compounds.
The composition of natural gas varies from source to
source. Some natural gases have a carbon dioxide content
as high as 30% or more. Other natural gases contain high
percentages of hydrogen sulfide, nitrogen, or helium. Prior
to being sold, natural' gas is processed to remove much of
the norifuel component since these materials will not burn.
Although the processed gas will vary in oilposition,.a typi-
cal composition of natural gas sold as fuel is shown in Table
2.
0
124 CH-09/Page 9
TABLE 2. COMPOSITION OF ATURAL GASAFTER PROCESSING FOR S LE.
Ethane
Propane
n-Butane
Isobutane
Bottled gas, or liquified petroleum gases (LPG), is a
mixture of propane, C3Ha, and'butane, C4Hio Propane and
butane are extracted from natural gas or obtained as 4y-pro-.
-.1-fr
educts of petroleum refining. These gases are com ss_ed .
until liquified and then "bottled" in steel cy ders. The
liquified gas readily reverts to the gaseous. form when the
pressure is reduced and the gas is consumed. Bottled gas is4
used in rural areas for cooling and heating, on house frail-,.
ers-, and on recreational vehicles.
Acetylene is a gaseous fuel that burns in an atmosphere
of pure oxygen to produce extremely high temperatures
(3000°C). The high temperature from tlfe:reaction of oxygen
And acetylene is used in the oxyacetylene torch a torch
that is useful for welding and cutting metals. The reaction
is as follows:.
2 HCIC H + 5 02 ----> 4 CO2 + 2 H20 + 620 kcal
Page 10/CH-09
125
CaO
4
In addition.to being used as a fuel, acetylene (ethyne),
C2H2, is widely used in polymerization reactions to form
plas.tics. Acetylene is made by reacting calcium carbide
with water. The first step in the production of acetylene
is the heating of lime.stone in a kiln to produce calcium
oxide:
--'tAC03
Limestone
C
Heat+ CO2
__Calcium oxide (quicklim.e)
A mixture of the-calcium oxide and coke is then heated in
an electric furnace to produce calcium carbide:
e . 2000 °C
2 C +:Ca0 CaC + CO
Coke Calcium Calcium'oxide A carbide
Finally, the calcium carbide is reacted with water to produce
acetylene and calcium hydroxide:
CaC2 + 2 H2O ---im-H=C-7CH+ Ca (OH) 2
Calcium.carbide
Acetylene
126'CH-09/Page
LIQUID FUELS
4 4
The important liquid fuels gasoline, kerosene, and
fuel oil are obtained from petroleum. Petroleum, as it
comes from the oil well, is called-crude oil. -It consists--
of a complex mixture of different types of hydrocar.bons
(compounds of carbon and hydrogen). Petroleum is foundin
porous rocks and ands; leis never found in underground
pools or lakes. A variety of methods are used to remove the
oil from the porous rocks and sands.
Crude oil is shipped by tanker or underground pipeline
to a-refinery for processing. In the refinery, crude oil
is heated to vaporize and separate it into fractions accord-
ing to boiling point. This -fractional distillation process
is much the same as that which will be used in onvf the
laboratories in this module.
The principal fractions obtained from the refining of
petroleum will now be considered. The first materials to
come out of the fractionating tower -are gase. These gases
are soluble in the crude petroleum and; therefore, are in
the liquid state. When separated in the refining process,
they are free to remain in the gaseous state at normal tem-
peratures and pressures. These gases, which are mainly pro-
pane and butane, can be liquified and sold as bottled gas.
These low-boiling gaseous hydrocarbons are,also the building
blocks.for making many chemical compounds. The second frac-
tion is aviation gasoline, automobile gasoline, and solventL
Ker6§ehe, the next fraction, consists'of compounds having,
from 10 to 16 carbon atoms. Most of the kerosene is con-
verted to gasoline by cracking the larger molecules into
smaller ones. Keroiene' major use .today is 'for jet air-.
craft. Fuel oil contains more. carbons than the kerosenes.
Page 12/CH-09
127444
%IP
I Ir
Fuel oil is used for industrial and home furnaces. Diesel
fuel is produced from the fuel oil fraction. Following fuel
oils, the ext fractions are lubricating oils and greases.
The material obtained from the bottom of the distillation
-tower-consists of asphalt, waxes, and coke. The petroleum
fractions and their main uses are given in Table 3.
TABLE 3. PETROLEUM FRACTIONS..
Fraqions'
,
Composition Principal Uses
Gas C1 ,- C4 Fuel*
Gasoline (C6 C9 Auto ile fuel, solvent naphtha
Kerosene '- Clo C16 J fuel, fuel oil, diesel fuel
Oil C16 C16 Diesel fuel, cracked to gasoline
Wax oil C18 C20 Lubricants, mineral oils
Paraffin wax C21 C40 Wax paper, candles
Asphalt . *. Roofing, road material .
Gasoline production through the refining process will be
' considered later in this module.
ORGANIC CHEMISTRY
All of the fuels considered so far in this module,
solid, gaseous, and liquid, are organic compounds, that is,
compounds which contain carbon. Organic chemistry is the10,
study of these carbon-containing compounds. There are
128
several differences between organic and inorganic compounds,
including the following:
All organic compounds contain carbon, and most contain
hydrogen. In addition, organic compounds can contain
nitrogen,-oxygen,\and th halogens (chlorine; fluorine,
bromine, and iodine). Although organic compouncB are
comprised of only these few elements (plus several
othe'ts occasionally), inorganic compounds can contain
almost any of the more than 100 elements.
Many organic compoundS are either combustible or decom-
posed by heat; most inorganic compounds will not burn
and are stable when heated.
Most bonding in organic compounds is covalent; most of
the bonding in inorganic compounds is ionic.
Water is a poor solvent for organic compounds; however,
it is a good solvent for many inorganic compounds.
In comparison to inorganic coppound reactions, reactions
involving organic compounds generally proceed more
'slowly, and they do not go to completion.
Since so few elements are found in organic compounds it
would be logical to assume that the're are relatively few or-
ganic compounds. HoWever, there pre actually hundreds of
thousands of organic compounds. Two principal reasons for
this largenilmber of organic compounds are as follows:
1. Carbon has the unusual ability to bond to itse24 by
covalent <bonding, thus forming long citIns,and rings.
, Each of two adjacent carbon atoms furnishes one or
more electrons to form 'an electron Oar or pairs in
the .covalent bond. Because of this bcinding ability,
there are long series of compounds,. with each succes-
sive compound containing one more carbon than its
Page 14/CH-09
t.
12p.
predecessor. Examples of these series are alkanes,
alkenes, and alkyles. The three types of bonding
found in organic Compounds.are summarized in Table
4.
E 4: BONDING IN ORGANIC COMPOUNDS.
Type of BondElectron-Dot
Structure Series-
ExamplePrope'rName
CommonName
Single bond
f
A
I 1
C: C-- Alkane H H1 I
H-C ---HI I
H H
Ethane Ethane,
.
Double'bond. I 1
--C::C--
.
Alkene
1
H H1.-
,H-C=C-H
-
Ethane.
Ethylene
.
Triple bond ---C: C--'11
Alkyne/c'H-C= -H Ethyne . Acetylene
4
2. The same kinds and numbers of atoms can be
arranged differently to form different compounds
called' isomers. Isoters are compounds having
the same composition and molecular weight, but
different properties (because of different
arrangements of the atoms). For` example, in
the gaseous hydrocarbon butane, which has the
formula C4Hio, carbon atoms must have four bonds,
and-eacilflY-dx-ogen-mus_t have one bond.
130CH-09/Page 1S
-
o a
The following examples arp ,Iwo ways, that -four carbons
and 10 hydrogens c-in.be arranged:
t
ctd
H ,
H C H
H. H .11 ,H1H!III I . I
H C C. C C --:H HCCCH1, I I I
I 1
6 c 0
H -H H H= H H
Normal butane Isobutane Onethylpropane)
The first structure is callednormal butane. It has a con-
tinuous straight-chain structure, with each carbon bonkle.to....
no more thantwo other cdrbOns. The 'second compopnd is
called isobutane, or met4r1propane..
in. .,
One of the carbon atoms n isobutane is bonded to three
other carbOns. These are two diStinct compounds (isomers)
as indicated by thei'r boiling points,as well as other prop-.
erties. ( Isobutane has a boiling point of'-11.7°C, whereas
normal butane has a bOiling point of 0.5°C.) Table 5 illus -.F'
trates the tremendous number of isomers possible in org-anic
chemistry. For instance, there are 62 trillion possible iso-
mers ,of tetraco ane. 0 0
Page 16/CH-09
e.
I .
6.
1
.TABLE 5. -NUMBER OF POSSIB ISOMERS OF'SELECTED ALKANES:.
V
Molecular-Formula Name
A Number of PossibleIsomers .
CH4
. C2I-le.
C3H8
.C4H10
.C51-112
46111.4v
. C7H-16
C8H18
Ci2H2.6
CoH42
C4oHe2
.. ,
.
.
,
,
ethane
lthane
Propane .
Butane
. Pentane
Hexane ....,
.
Hepfane
Octane
Dodecane.
Eitosane
Tetracontane
,
./
.
..
. 0;
0'
1 0.
,
. . . 2. .
.
3. . _
5.
.'9
&.
.
.
355.
.366,319'
.
62,491,178,805,83)
- The
laolecular formula does not give enough information
..
to be v ry useful in working with organic compounds, there-:.
fore, "structural formulas" are used. A.dash () is used to
represent a bond between pairs of atoms rather than using two
dots to represent the two electrons. The following formulas
can be used to represent butane: ..-
. ...,--
1. A simple'Molecular formula:
C4Hio
2. A simplified structural formufa:
CH2 CH2 CH2 - CH;
)1 3 2
0
4
A
3. A full structural formula:
H H H H
H 7CCCC H'.I I I
H H H H
When first starting to study organic ,chemistry,-it is best
for one to'use the full structural formula. After some
familiari.ty with writing structures, however, the simplified
structure,is sufficient." The simple molecular prmula nor-
mally is not very useful. 1,4. .
N
CLASSIFICATION OF ORGANIC COMPOUNDS
Qrganit eompounds Olissified into two general'
groups: aliphatic' compounds and arbtaii"ccompounds. -":ALi-
phatic compounds are straight-chain compounds, although .a
few cyclic(or ring) compounds that chemiCally resemble
straight-chain compounds can be straight-chain or branched.
Aromatic compounds have a special six-member hexagonal.car- ,
bon ring1Called She benzene ring. The aromatic hydrocarb s
form three common series: the be zene, the naphthalene and
the anpracene series. The aliph fix hydrocarbons also form
three series: the alkanes, the alk nes,-and the 'alkYnes.
The sources, chemical reactions, physical properties, and
nonmenclature of some of the members of these Aeries will now
be donsidered.
Page 18/CH-09
1 a 3'
ALKANE SERIES'
The alka ne series of hydrocarbons are the simplest-
organic compounds. They contain only single bonds and only
'two elements: 'carbon and hydrogen. TAe series is.also bailed
the methane series (after the first member of the series) and
the paraffin series (because of the stah'ility of members of
the series which resembles paraffin one of the highest mem-
bers of the series). The members of this-series thave the
general formula of CnH 2n+2, where n can be any number/ If.
= 1, the compound is CH4; if n = 2, the coTpounds is C2H6;
if n = 3, the compound is 3H8, and so on.
The first 'member of-the alkanes is methane (CH4), x
colorless, near ly odorless,gas. About 90% of the gas in ,
natural gas is methane. Methane is formed by the decomposi-41tionof organic matter, such as in marshes; therefore, the
gas is sometimes called marshgas. t,also is formed in coal
mines (coal gas), where it can form a dangerous, explosive
mixture with air. Since methane isaljost odorless, mercap-
tans are added to give. natural as a. detectable odor so that
is safer.
The first four members of the alkane family are gases.
,Alkanes containing 5 to 17 carbon atoms are liquids at room
tomperatilie,"wheea those having 18 or more carbon
are' solids:
The a lkanes
,
all of which are obtained froth petroleum,
are usually consume mixtures.
134
0
CH-09/Rage 19
NOMENCLAtUR
Many of the more common organiC Compounds were named
long -ago. A$ the number of known compounds grew, however,
a systematic means of naming compounds became neFessary.
AS early as 1892, a committee of chemists met at Geneva,
Switzerland, to develop this method. The most recent group
to prbpose, names met in Amsterdam in 1949. This system of
naming 'organic 'compounds, knoutn as the IUPAC (International
Union of Pure and Applied Chemistry) system, currently
in use. Unfortunately, both the common name and the propeir
name for many compounds are widely used; therefore,-bothto
must 1e learned.
The fist four members of the.alkanes have only common
names: methane, ethane, propane, andbutane. (Notethat
all, of the alkanes encPWith the,suffix,-ane.) The next
members follow a system in which he number .of atoms present
in a continuous chain is'indicated,by a Greek prefix, fol-..
lowed by ihe,-ane (ori-ne) suffix: The following are
examples: '
.C51-112
C6H14
C7H16
is pritane' (penta is 5).
is hekane (hexa is 6).
is heptane-(hepta is 7).
C81-48 'is octane (octa is 8) .
The unbranched, or continuous, chain alkanes are called,
normal,""and the prefix n- is used (for example, n-butane).
Alkyl groups, or radicals, have no independent existence',. .
but they arerused naming organic compounds. Removal of.
one hydrogen from an alkane'gives an alkylgroup, which is
named by replacing the -arse of the alkane with -yl: The
.following:Are.examples: .
Page 20/CH-09
H H'
' I I
H C H becomes H* C or CH3I
1-
H
Methane Methyl
H H H
0 . 1 . I
H --C = C H becomes H C C Gr C2H5.1 I I . I
H H H H
.Ethane Ether
The following are examples of using the alkyl g.rou s in
naming compounds:
CH3Br Methylbromide
CiH5OH Ethyl alcohol
CH3 CH2 CH2 n-Propyl iodide\
The following ItIPXC rules arehlflin naming orga4c.
compounds:
1. Determine4the longest Rtntinuous carbon chain in the :
compound and dame 4t.-asan alkane. The, name of this
,45 chain is' the basic Dime of the compound.,
2. Number the carbon atoms.in the chain from one end or
the other so that the alkyl groups or o er atoms have
the smallest possible numbers..
/ 3. The position of each.r.
ubSstituent is designated:by the.
nutber of .the carbon atom to which it is attached.
Hyphens are usedto aseprate nuMbers from names of. .
subtituents.
ft
, 13
CH-V/Page 21
r
ti
ti
'4. If identical groups Appear More than once, the number
of the carbon to which each is bonded is given each
time. If identical' groups appear on the same carbon,
the number is repeated. Numbers are separated from
each other by commas. The number of identical' groups
is indicated .by prefixes: di-, tri-, tetra-, and so
on.
S°. The name is written in a continuous manner hat is,
there are no spaces Left in the name):
6, If more than cwe alkyl group is present, they are
named in alphabetical order (for example, ethyl before
methyl).
The preceding rules are illustrated below:
CH3
1
CH3 C 2,2-Dimethylpropane
CH 3
The longest carbon chain is three; therefore the basic
name is propane. ,Two methyl groups are sp carbon num-
ber 2; therefore 2,2-di- is used.
CH3
CH3 C CH2 CH3
H
2 - Methylbutane
The longest carbon chain is four; therefore the basic
name is butane. Numbering from left to right would
place the methyl group on carbon number 2. (Numbering
from right to left would place the methyl gr6up on
carbon number 4. Since gpur is larger than two, 4-
methylbutane would be incorrect.)
Page 22/CH-09'
(
137
H..1
CH3 - C - CH3 - Cl 1,2-Dichloropropane e
111
Cl
The longest carbon chqin is thre erefore the basic
name is.propane. Numbering from right to left gives
the smallest numbers (1 and 2), rather than 2 and 3:
One chlorine is on carbon number 1 and one chlorine is
on carbon number 2. Since there are two chlorines,
di- is used.'
CH3 Cl
1
CH3 CH2 C CH2 C CH3. 2-Bromo,2-hloro,4-methylhexane
H Br
4
The longest carbon chain' is six; therefore, the basic
name is hexane. Numbering from right to left gives
the smallest numbers. Both bromine and Chlorine are
on carbon number 2. (Bromo appears in the alphabet
before chloro.) A methyl group is on carbon number
4.
The most important use of the aikanes, as indicated
earlier, is for fuel. As an illustration, of the combustion
kiof alkanes, consider-th combustion of
C3H8 4' .5 2 3 CO2 + 4 H2O
Propane Oxygen Carbon Waterdioxide
138 CH-09/Page 23
ALKENE SERIES
Members of the alkene series have at least one double
bond. This series is also known as the olefins, or the
ethylene series, after tlie first memb.?r of the group. The
general formula for the series is CnH 2n . The first three
compounds in the series are gases, whereas the-higher mem-
bers are liquids and solids. Ethylene is usediti artifical
ripeningof fruits since it destroys the green chlorophyll,
changing the fruit from green to yellow. Its major uses are
,as follows: for production of ethylene glycol,_for use as
antifreeze, and fot synthesis of plastics.
The IUPAC rules for naming alkenes are the same as
for alkanes except for the following rulei:
1. The longest chain containing the double bond is num-
bered.
2. The -ane is changed to -ene for alkenes.
3. The numbering begins from the end of the chain which
allows the dolible bond to be located on the smallest
numbered carbon as possible. The double bond'is lo-
cated by the number given to the first arbon of the
bond.
4. The-prefixes di, tri-, and so on, are U'ed when more
than one'double bond is present, and they appear with-
in the name just before the -ene.
The preceding rules are illustrated with the following ex-
,amples:
H H ,HHHI I I I I
H - C - H H-t-C=C- HEthene Propene
(ethylene) (propylene),,
Page 24/CH-09
129
k-\\N
I
I
I
I
I
I
I
Or CH3 - CH2 - C.= CH2
I I
H H
I .
I
According to the IUPAC rules, the number starts from
the smile which will place the smallest number next to the
carbon-'carbon double bond. Thus, the correct name for the
first si\ructure is 1-butene -(not 3- butane). Note that this
is an example of another type of isomer.
II
*3-
-*
The-first two members of the series; ethene and propene, are
rshown above. It is not necessary for numbers to be 'used to
locate the double bond since there are no other possibilities
for the location; In ethane, the bond. must be between the two
carbons, and; in propene, the bond can be between either4pair
of carbons.' However, the positions are equivalent. Remember
that the molecule is free to rotate. If the bond is on the
right pair, arotatioft of 180° places the bond on the left,
and the moleeule'is the same one. CoMmon names for these
compounds are ethylene and propylene.
There are two possible compounds of molecular formula
C4H8: 1- butane and Z-butene. These compounds are shown.
below:
H H H H.
1-,Btene 1- Butene
'H H- 'H H H H.
1 1 I II
H C C = C 7 C H OT CH3 - C C 2 CH3
I
H
2- Butene 2-Butene
140CH-09/Page 25
4
H H H,
I I I I '
H -C=C-C=C- H 1,3-Butadiene
This compound has four carbons; therefore the basic name
is butane. Since there are double bonds present, the name
is butene. The two double bonds are located adjacent to
the numbers 1 and 3 carbons. The prefix di- is inserted
before the -eneto reinforce the fact that there are two
double bonds in the compound
CH3 CH3
CH3 CH - CH2 2,4-Dimethyl-l-pentene
The basic name of this compound is pentane, since it has
five carbon atoms in the longest chain containing the double
bond. However, the name is pentene because of the double
bond. Two methylaroups are-prelmrrt---ane-on carbrOn-number-
2 and one on carbon number 4. Thus, 2,4-dimethyl is part of
the name. The double bond is adjacent to the carbon numbered
1. This is indicated in the name by the 1 appearing just be-
fore the pentene. Note that this is not 4, since the double
bond is located by the smailest'number.possible. Therefore,
the numbering of the carbon atoms begins on the right rather
than on the left. Note that in all cases the carbon atom
has four bonds.
ALKYNE SERIES
The.alkynes, or acetylenes, are ,unsaturated hydrocarbons.
that contain atriple bond, dr three pairs of shared elec- /,
trans betvieervadjacent carbon atoms. The general formula
Page- 26/CH -09'
141
9
for alkynes,conitaining one triple bond is C_n H2n-2'
The first
member of the series is ethylene, commonly called acetylene:
H H Ethylyne (acetylene).
]The alkynes area named by using the same rules as those for
the ethylene series, exept that -yne is used to replace -ane
of the basic na1ne. Examples of members of this series-are
given below:
CH3 CC H Propyne (methylacetylene)
CH3 C i C --CH3' 2-Butyne
CH3 CH2 CH ,C C H 3-Methyl-l-pentyne
CH3
CYCLOALKANES
Cycloalkanes are saturated hydrocarbons that have ring
structures. The first three members of this series are
shown below:
CH2 CH2, CHf CH2\/ \
I I
/ ,
CH2 CH CH2 CH2 CHi CH2
\ /CH2 CH2
Cyclop-ropane Cycl \f) butane Cyclopentane
CH-09/Page 27
"142'
J
\ These rings are under considerable strain and, therefore, the
cycloalkanes, in general, are rather reactive.
AROMATIC HYDROCARBONS
The aromatic hydrocarbons are ring hydrocarbons that
contain the benzene _structure. These hydrodarbons are ob-
tained from the destructive distillation of coal, which pro-..
duces the coal: tar containing the aromatics. As the demand
for the aromatic compounds has grown, additional supplies
have been obtained from petroleum. Maly of the aromatic
compounds have a rather pleasant odor hence the name
"aromatic." Benzene is a clear, colorless liquid having
a fairly pleasant odor. Excessive inhalation of benzene
and most aromatics should be avoided bkause of their toxi-
city. Benzene freezes at 5.5 °C, boils at 80.1°C, is insol-
uble in water, and is an excellent solvent for fats, waxes,
and resins: Benzene and other aromatics have a high anti-
knock value; therefore, they are used in gasoline to raise
the octane number. Larger amounts of the aromatics must be
used in no-lead gasoline than in leaded gasoline which
causes the cost of Tro-lead gasoline to be higher than the
leaded.
The molecular formula for benzene is C6H6. Three com-
monly used structures gpr benzene are given on the following
page.
Page 28/CH-09 143
Hiv
C
H C /f H
4
or
6,s
(2) (3)
Structure number (1) indicates that the six carbons have
alternating single and double bonds which would indicate
that benzene__ should befairly_reactive since it pos'sesses
the double bonds. However, this is not the case; benzene
is rather stable. The bonds are equivalent to each,bther.
NOMENCLATURE OF AROMATIC COMPOUNDS
An element or radical may replace'one or more of the
hydrogen atoms of benzene -to give compound; such as the
following:
Cl
Chlorobenzene
NO2
t
Nitrobenzene
CH3
Methylbenzene(toluene)
144. .
' CH-09/Page 29
to
CP
These compounds are named as substituted benzene. The group
C6H5 (benzene minus one of'ts hydrogens) is known as the
phenyl radical; therefore, the first compound can also be
called phenyl chloride. Names of this type are encountered
occasionally. When two or more substituents appease on the
ring, their relative positions must be designated. This can
be done by using the prefixes, ortho- (o), Inca- (m),Noawr-
paral" (p); or it can be done by locating the substittients
,On the ring by numbers. The six carbon atoms are numbered
so that the' smallest,possible numbers. Are used. Suppose
that there are two methyl groups attached to benzene. These
are three isometric forms of these dimethylbenzenes, or
xylenes:
CH3
CH3 CH3
CH3
(o-Xylene m-Xylene p-Xylene .
(1,2-Dimethylbenzene) (1,3-Dimethylbenzene) (1,4-Dimethylbenzene)
' In the Qrtho position, the -two substituents are adjacent to
each other (on the numbers 1 and 2 carbons). In the meta
position, the two subst ti.lnts are separated by one carbon
(on the number 1 and 3 carbons). In the para position,.the,
two substituehts are oppo te each other (on the numbers 1
and 4 carbons). -
Toluene, aniline, and phenO1 are three Common names
given to. important derivatiei of benzene. Their structures
are as follows:
Page 30/CH-09
I
s'
41.
k
Toluene(methylbenzejle)
NH2
Aniline
4't
Derivatives of these compounds are named by considering the
number 1 carbon to'the be one with the group 'that gives the
compound its name (that is, the carbon containing the CH3,
NH2,or OH group).' Examines of these substituted compounds
. are given below:
O
OH.
Phenol(hydroxybenzeN)
Br
Br
4-Nitrotoluene 2,3=Dilyet-MOaniline
(p-nitrotoluene)
OH
2,4,61Tribtomophenol',
The order if naming.a cpMpo n4 is alphabetical when three
different substituentccUp ` 'tions on the ring.
Aromatic compounds' can Oantain mere than one benien& ring.,
Examples include naphthalene with con nsed benzene ,
rings, and anthracene, with three condensed be zene rings:
CH-09/Page31
5 4
Naphthalene
5. 10, '4
Anthracene
The numbering system indicated on the structures is used to
name substituted naphthaleneS and anthracdnes. Consider the
following substitdted naphthalenes:
CH3
- CH3
SUBSTITUTED HYDROCARBONS .
1,5-Dimethylnaphthalene
Substituted hydrocarbons are h drocarbans in which atNv
least 'one hydrogen 'atom has been replaced by.a'functional
group. Some of the major substituted hydrocarbon classes
and functional groups are identified' in Table 6.
The substituted. hydrocarbons containing fluorine are an
important group'of compounds, esp cirally those containing
more than -one fluorine atom.. These p lyfluorinated hydro-
carbons, which commonly exist as gases, are extremely inert,
nontoxic, and noncorrosive.' 14 the liqUid state they have a
low boiling point. These properties make the polyfluorinated
hydrocarbons_ useful as refrigerants. They are commonly known.
by their trade name, Freon.
Page 32/CH-Q9
147
TABLE 6 CLASSFS OF SUBSTITUTED HYDROCARBONS.ANDTHEIR FUNCTIONAL GROUPS.
.
ClassFunctional
GroupGeneralFormula Structure
.
Name
Alcohols
Phenols
Ethers
Aldehydes
Ketones
Acids
.
Esters
0-11
-0HC 0 C
C-....H
.,,C=0 ,
,.oC(..
N Oil
0 -) \C' t'
NO ir---y.
R 0 11R 0 11
R d Rii3O
R Ct /..
H
,CO.=
oR C'
N OH.0
RC ' 4` 0 R
C2115011
C6115011
CH3-0 C
0
113
°CH -c3 ..
11
gCH 3,--C CH 3
. 0C11.C ''.0H
0C113C
NO - C}13N 0 C11,
Ethyl alcohol
Phenol (carbolic acid)
Dimethyl ether
Acetaldehyde
,
Acetone.
Acetic acid
.
Methyl acetate
Amines
Halogens
NH;
T,C1,Dr,or I
_
R-11112
R X (whereX is a halo-gen) -
CH 3CH2NH;
CH3 Cl
Ethyl amine
Methyl chloride. .
I
The alcohols, aldehydes, ketones, and acids are inter-
related. Upon oxidation, alcohols can produce aldehydes or
kdtones, depending upon the alcohol. Further oxidation will
convert the aldehyde to an acid. For example, upon partial
4 oxidation, ethylene glycol produces glycolic aldehyde which
can be further oxidized to produce. glycolic acid, as shown in,
the following equation:
148 CH09/Page 33
H H H H H /r.---
_ I --I Oxidation I. I Oxidation I ,0H-7--C C H H. C C-0 HCC-'--OH
I I . I I
OH OH OH , .- OH
Ethylene glycol Glyoclic aldehyde Glycolic acid
Ethylene glycol is widely used, as the heat transfer medium
in solar energy panels. If.5the ethylene glycol is exposed
to air (oxygen), it will undergo the, undesirable reaction
indicated above and produce glycolic acid. The glycolic
acid is corrosive and produces damage to pumps and other
components of the solar system.
GASOLINE PRODUCTION
Now that Organic chemistry lias been briefly considered,
gasoline production can .be studied. The supply of gaslli.ne .
from the.fractional distillation of petroleum, called,
straight-run gasoline, is'inadequate in quantity and quality
for supplying current About 40% of all petroleum is
converted't9 high ,grade gasoline. A variety of-techniques
are'used to supplement straight-run gasoline.,
'Gasoline is composed of a mixture of hydrocarbons,_which
includes alkanes, alkenel, cyclic compounds, and aromatics.
Examples of these hyd/Tocarbons are as follows:
t
Page 34/CH-09
4
149
'7)
ig141:11i°VR
H H H tH HIIII111H-- C--C--C--C--C--C--CH
1,1 I' I IHHHHH H
n-Heptane (alkane)
CH3 H H,I I
CH3C GC CH3. I I
HI
CH3 CH3
Toluene,... (aromatic)
'H H H H
I I I IHCCCC=CH2l I'
H H H
ISo-octane (branched alkane) -I-Pentene .(alkene)
Methylcyclohexane
Straight-chain hydrocarbons, such-as heptalg,e, ais.e obtained
in straight-run gasoline. In general, they burn too fast
for smooth combustion. They can ignite prematurely in the
engine, causing knocking. This can result in engine damage
and lo,s of lower. On the Other hand, branched alkanes,
cycloalkanes, alkanes, andaromatics'burn mo e evenly and
witli-out knocking. The octane number is a atiq used to
'indicate a gasoline's tendenCy to knock.- On the octane'
nheitane is assigned a value -of zero, whereas.iso-
-octailfs. assigned a value of 100. A' gasoline with an octane
rating of 90. would have the Same tendency to knock as would .
a mixture of 90% isooctane -and 10% n-heptane,.. Octane tests
` are conduCted iniktesting internal combustion engines. Blends
of n-heptane and iso-octane are compared (in performance) to
150' CH-09/Pg0 3S
4
the gasoline being tested. It s_possible to have octane
ratings of over 100 that is, .the gasoline will knock evenless than_ilo-octane. Aviation .gradg fuels.generally have
octane numbers .over 100. Octane ratings can be improved byA
the use of additives. Tetraethyl lead'(T;L) is commonly used
to reduce_the_knocking of_afuel, thereby increasing its
octane rating. Table 7 contains a listing of octane numbers
of some hydrocarbons with and iiithout tetraethyl lead.
TABLE 7. OCTANE RATINGS..
Hydrocarbon,,
Formula ml TEL/galldn
0 ,.. 3
n-Pentane C5H12 61.7 88.7
n-Hexane C6H1,4 24.8 .65,3 1
n-Heptane C7H16 0.0 43.5.
-Toluene ,'.
--), C7H8 103.2 -111.8
'n-Octane.
CEIHI8 -19.0 25.0
Iso-octane C8H18 100.0 115.5
'IsopropylbenierwP C9H12 113.0 - 116.7
1pote. the'marked increase in octane ratings with the
addition-'of TEL, especially for the straight-chain (normal)
hydvtarbons. 'In addition, the effect of branching in the
alkites can be seen by comparing the octane ratings of n-0
octane and iSa-octane. These compounds, differ. in octane
-ratings (without TE1) by,119. In order to carry 'away the
'Page 36/CH-09
151
T.
lead and prevent unwanted deposits of lead in the engine,
ethylene dibromide is added to leaded gasoline. The lead
reacts with ethylene dibromide to form PbBr2, which is ex-
.-hausted into the.atmosphere. In an effort to eliminate '
the environmental hazard of emitting thousinds of tons of
lead into the atmosphere yearly, later model automobiles
use unleaded gasoline. The elimination of lead compounds
.from gasoline requires that the automobile have a lower
compression ratio so that the lower octane gasolines may
be used. The Lower compression ratio results in decreased
power of the automobile. To compensate somewhat for the
loss in octane rating by the elimination of lead compounds,
the more Costly aromatic hpdrocarbons must be included in
gasoline blends,-accounting for the greater cast ofunleaded
gasolipe as compared o leaded. Previously, the aromatic
compounds were removedfrom gasoline during the refining
process,so they.could be used to produce a variety of prod-
ucts. This increased competition for aromatics, has driven
their price up, and this increase is reflected in products
made from aromatic hydrocarbons.
Normal centane, C16H34, is 'used as the standard for
rating diesel fuels. High octane numbers are not desirable
for diesel fuels that come from the gas oil fraction during
the fractional distillation of petroleum.
A numbef of methods are used to increase the yield
of gasoline from petroleum and to increase the octane number.
In the fractional distillation of petroleum, relatively
large quantities of the longer-chain hydrocarbon& are obtained.
-These long7chain,hydrocarbons can be broken down into two
jor more smaller molecules in a process called catalytic__ _
cratking.', Pressures as highas 1200 pounds pex square inch
and temperatures up to 1000°F, along with a suitable cat,lyst,
152
Z.
CH-09/Page 57,
are used in the cracking operation. A variety of products
are available from the cracking process. For example,
C15H32 can be-iracked to produce compounds containing six,
seven, eight, or nine carbons. The straight-chain compounds
can be reformed or rearranged into cyclic or branched com-
pounds to have a gasoline of higher octane number. In the
cracking operation, a molecule of centane, CI6H24, can be
spit into a molecule of octane and a\molecule of unsaturated
octene:
CatalystCl6H34 C8H18 C8H16
Heat, press
Centane n-OcArne- 'Octene
Catalytic,crackingis the most important technique.of in-
creasing the yield of, gasoline from petroleVm.
Another method of increasing the yield of gasoline
is reforming. In reforming, a straight-chain hydrocarbon
is converted into a branched hydrocarbon. Consider the
reforming of n-butane into tsobutane when heated with a
suitable catalyst:
H H H
ICatilystCH3 C--CH3 + H2
till HeatH H H H CH3
n-Butane Isobutane ' Hydrogen
Polymerization is used in the refining process to com-f
bine small-chaintydrotarbons into longer-chain compounds.
It is essentially4the opposite of cracking. The initial
.
Page 38/CH-09
1 53
ti
fractional distillation of petroleum yields propane, butane,
acid other short-chain compounds that are not useful as
I
gasoline. They May be polymer,ized, however, into longef-,
chain corounds. For example, n-propane'can combine with
1-buteneNto produce n-heptane:
H H H
I I
I I I
+ CI
= CI I
CH 2CH3CH2-CH2C1--CH2--C
H H H H H
n-.Butane 1-Butene n-Heptane
2-CH3
Still another method of increasing the yield ofigasoline
is dehydrogenation; this involves removing hydrogen from
saturated hydrocarbons, such as propane and butane, to form
unsaturated hydrocarbons (compounds with double bonds), such
_54 propene and butene: The unsaturated hydrocarbons can
then be used in polymerization, as illustrated previously
with 1-bZitene:
Alkylation is similar to polymerization in that smaller
molecules are combined to produce larger hydrocarbons. in
alkylation,-b-rahehed alkanes are combined with-branched
alkenes to form4longer,chain compounds. Alkylation is illus-
trated by the combination of isobutane and isobutene to
form 2,2,4-trimethylpentane:
CH3 .
CH3 C H + CH2=CC1-13 .-
Catalyst
1
CH3 CH3Heat
CH3 HI
CHf-C--CH2-C--CH3
.._ I
CH3 CHI
Isobutane Isobutene 2,2,4'-TriMethylpentane
1541CH-09/Page 39
/
A
.
In summary, the fractional distillation of petrbleum
does not prOduce the desired distribution of compOUnds;
specifically, much more ga'soline is required, ¶o increase
the yield of gasoline, a inumber of methods are used, in-
ciuding catalytic cracking:, reforming, polymerization, de---;
hydration, and alkylation!
As indicated earlier, the liquification of coal to
form petroleum-like products will be required in the future.
Because-of the absence-of petroleum deposits, Germany
during World War II developed several processes for the
production of liquid fuejs from coal. In one of these, coke
and steam are used to,produce carbon monoxide and hydrogen.
The carbon monoxide is then reaciedwith an excess of hydro-
gen to produce hydrocarbons that can be used as liquid fuels.
The reaction is as follows:
st8 CO + 17 H2
CatalystC8H18 + 8 H2O
Heat
Carbon Hydrogen. Octane Watermonoxide
The catalyst used is thorium oxide, ThOz, and .the temperature
is 250°C. This reaction is knbwn as the Fischer,Tropsch
process: .
- Another method for.the liquification ofcoal, known
as the Bergitis process, combines hydrogen and carbon did
rectly under high pressures sand temperatures:
Page 4-0/cH-09 155
erf
F8 C + 9 H2
e20, MoO2
700 atmospheres400°C
k
C8H18
Carbon Hydrogen Octane
The Bergius process can be used to produce diesel fuel, jet
'fuel, and gasoline. The cost of gasoline, when produced from
coal, is not now competitive_ with that produced from petrO=
leum.
ALTERNATE ENERGY SOURCESrt.
As already indicated, the near exclusive dependence
upon fossil fuels and the acceleratinvutilization of these
fuels have resulted in an energy cri,is. The availability
of natural gas and petroleum is neaiing its peak; in the
future, less of these fuels will,be available. Therefore,
considerable pesearch and development is being conducted on
,alternte, or.unconventkonal, energy sources. Certainly
coal gasi:ficationAand coal liqUification, (which were
cussed previously) can be considered to be unconventional
energy Sources. Additional alternate energy%tources include,
methanol, ethanol, hydrogen, bkomass,,solar, nuclear, wind,
tidal power, hydroelectrkc, and geothermal. Nucleir,issdon
aid fusion as sources of energy will be considered in a
later module.
/111111.
156CH-09/Page 41
ba.
a
METHANOL
4
Methanol (methyl al6ohol) has been used as a fuel for
over a century. It is a liquid fuel that could be used in
internal combustion engines to power automobiles without
major modification of-the engine. Methanol (also called.
wood aleahol)can-bemade from wood, coalTother-iossil/1
fuels, farm wastes, and municipal wastes. It burns with a
emissionclean, blue flame, with no mission of sulfur oxides or par-
ticulates. Although it is'being considered primarily as ,a
replacement for gasoline, methanol could also be used for
space heating and electric 'power generation. Methanol, when
used as a gasoline additive in present engines without mod-
ification, increases engine power, and economy while decreas-
ing engine emissions. anol is,a liquid at room tempera-
ture and can be trans rted and handled in much the same
manner as gasoline. A gasoline-methanol mixture containing
15% methanol appears to be they optimum mixture. With th'ss_
mixture (in an unmodified engine) carbon monoxide emi ions
decrease by as much as 70%, fuel economy improves by 0%,
and acceleration improves/by 7%, as compared to gasoline.
Methanol has an octane number over 100; therefore it,can be
used to replace tetraethyl lead as -an antiknock agent. Its
use as a mixture could stretch gasoline reserves. Methanol's
low, energy contentapproximately half that of gasoline) in-
creases its relative distribution costs. However, a disadvan-
tage ot' methanol' is its corrosive tendency. The two primary
limitations to its use are price and availability. As the
flprice of, gasoline continues to increase, methanol will be-
come attractive as a fuel Tassuming the price oi methanol
,does not increase as rapidly). By using municipal wastes to
produce it, methanol would become much more available and
Page 42/CH-09
157
less expensive. It is estimated that, if 'all the municipal,
wastes in the United States were used-to.produce methanol,
enoUgh'would be available to supply nearly 8% of the'fuel
required/yearly for transportation.. Another source of
methanal--c-otaci--conte-irromwoo-d-,wkri-eh-- wouldbe=produced on
energy plantations. These commercial forests would, in
effect, be solar converters that could transform solar en-
ergy into wood and then into methanol. The city of Seattle,
Washington, is conducting a study of'the production of
methanol from the city's solid waste. The volume of waste
needing to be disposed of is greatly reduced, while, at the
same time, 100,000 tons of methanol could be produced.
ETHANOL
Another alcohol with a potential for use as a fuel is
ethanol (also called grain alcohol, or ethyl alcohol).
Ethanol can be produced by the fermentation of grain. Any
grain can be used, but the most economicar is milo. The
first step in the production of ethanol from grain is the
conversion of starch in the grain to sugar:
2 C6H1005 + H2ODiastase
)1- C12H22011
in malt
Starch Maltose
The enzyme diastase converts the starch to the sugar maltose.
In the second step, the maltose is converted to glucose with,
the aid of the enzyme maltase:
158 CH-09/Page 43'
,
G12H22011
4).
Maltase+ H2O > 2 C6H1206
Maltose Glucose
Finally, the glucose is-converted to ethanol with the aid ofo
the enzyme zymase:
C2H1206 > 2 C2H5OH + 2 CO2
Glucose Ethanol 4
The by-product of the fermentation, carbon dioxide, is sold
as "dry ice" in the solid form or in tanks as compressed gas.
The kermentation,process produces ethanol of approximately
10% concentration. The ethanol is separated from the EePmen
tation mixture by fractional distillation.
In addition to being aade in the fermentation process,
ethanol is also currently made from ethylene.. The cost of
ethanol made from ethylene is approximately half the cost of
ethanol °made from grains. A present,-it is uneconomical to
make ethanol from grain in comparison to the ethylene pro-
cess. However-, no real advantagc isobtainedin using
ethanol made from ethylene as a fuel,' since'ethylene is a
hydrocarbon just as gasoline -is. To move from dependence
on petroleum, the ethanol used as a fuel must be made from
fermentation of grain. A blend of gasoline-ethanol cohtain-
hig 10% ethanol (called gasohol) is, being fleet tested. A
blend of this composition would/raise the, nice of a gallon
of gaSoline by three centsa gallon. No advantage of using
ethanol.is seen in terms of drivab4ity or reduced emissions.
Solubility problems associated with gasoline, alcohol, and
water would present problemssof:handling since storage
. Page 44/CH-09
1599
ro
C
P facilities would require some way to prevent water contamina-
tion because of the hygroscopic (water-attracting) nature of
ethanol. Cold weather separation has been a problem, az well
as slow vehicle warm-up.. Ethanol has an octane value of 106;
therefore i tcan be used to replace, at least a portion, of the
tetraethyl lead'in gasoline. As with methanol, corrosion
problems are associated with the introduction of ethanol into
the, internal combution engine. In summary, thei.e are no
important technical advantages to the use of ethanol as an
automotive fuel, and until the\cost and availability of gaso-
line become significant factors', the use of ethanol will be
limited.
HYDROGEN
,-The term "hydrogen economy" refers to the concept in
which conventional fuels would be replaced by hydrogen. This
concept as appeal because, potentially, it can solve the
pollution problem. When hydrogen burns, the product is water;
therefore,- unlimited amounts of hydrogen could be burned with-
out polluting the'atmospheike. The reaction is simple:
2 H2 02 2 H2O + Heat.-
Hydrogen could be transported in the pipelines currently used
for natural gas. In heating applications, it would require
little venting since carbon dioxide and particulates would
not be emitted only water. Hydrogen can be burned in jet
engines and, with modification, in the automobile engilie.
MoZt of the hydrogen produced today is made frOm,methane.
160 CH-09/Page 45
If hydrogen %Fere to become a useful fuel, it could no longer
be made from methane, since there would be no,advantage of
converting the foSsil fuel methane to hydrogen. The best ---/
,source for hydrogen is from the electrolysis of water In
electrOlysis, an electric current is passed through water,
and the water'molecules are broken down into hydrogen and
IY6rgen gases: The major problem of the hydrogen economy is
that electricity must be used'to produce the hydrogen. The
advantageS of the hydrogen economy can be realiied only if
an inexpensive method -.Qprodlicing electricity is devised,
such as by solar energy or nuclear energy. Even if all fos
sil fuels were depleted, modern:society,could exist in much
thesame manner as it is now by utilizing hydrogen that is,
if adequate electrical energy were available.
,BIOMASS
Municipal wastes, including garbage, trash, and sewage,'
have traditionally been discarded. The volume of waste grows
each year, making disposal difficult. This waste can be used
to produce valuable products. The,decay of organic matter by
bacteria in the absence of air results in methane gas.
In the presence of oxygen, methanol can be produced. A cer-
tain part diTthe municipal wase-can be incinerated to pro-
duce steam for generating electricity. As fuel costs and
V_waste disposal costs rise, more cities vii/1 likely start.pro-
ducing'fuels- from their wastes.
ne means of achieving a long-term, perpetual methane
econom to,convert. a continuously renewablenonfossil
,carban to ynthetic gas. The renewable carbon could come
'Page 46/CH-09 161,
111
from plants commonly referred to as biomass. Sources of
biomass include trees, plants, grasses,.algae, or wa er
14plants which are produced from sunlight by photosynth s-is.
Tremendous quantities of these plants would be required to
produce energy at the level of current consumption. The
-tec-hisology for biomass woductian-and-gasIfieation-is-cur-
rently available and should be competitive ith gas_derive'd,
from coal. Table 8 lists some examples'of f 1 gas prOdu.c-
from.biomass.
TABLE 8. EXAMPLES OF FUEL GAS PRODUCTION FROM BIOMASS.
BiomassConversionReaction
.
'Conditions- FuelProducts
Pine bark
Rice straw
Wood
Water hyacinth
Seaweed algae
Pyrolysis.
Pyrolysis
Digestion
Digestion
,Digestion
900°C,
200-700dC .
30°930 days,Intermediafe
48°C,4028 days
33°C, 20 days4
Low Btu gas, char, oil
Low Btu gas, char,.oil
Btu gas ,
Intermediate Btu gas
Intermediate Btu gas ,
Water hyacinth and algae are.high producers of organic
materials. Algae prpductiOn is 73 tons/acre/year (uncle'
ideal conditions), whereas water hyacinth production in
Mifsissippi approaches 15 tons/acre/year. Co1nercial con-.
veriion of.biomass is expected by 1985.
Y
162 CH -09 /Page 47
A
GEOTHERMAL
Geothermal energy has the potential of providing a
much greater fount of energy than is now available from
this source. Fifteen countries have operating electrical
generating plants of are constructing plants utilizing ged-,
thermal steam. At many geothermal. sites, steam is led di-
rectly to the turbines for electricity%production. Muchof'
the western United States has. underlytig hot-rock formations.
It_filay be possible. to drill a well into the thermal region,-5
pump water into the well, and remove steam from anothef well.
The ultimate potential power generation available'from geo-
thermal energy is unknown, but this source may provide a sig-
nificant amount of energy in the future. ,111
1
SOLAR ENERGYL.._
ISolar energy haS been described as a virtually infinite
..
source of energy that is free. Howevei, the applications of--..-
solar energy have-been hampered by the fact that sunlight is
diffuse and intermittent. A large land area is required for,
solar collectors, and means must. be provided for energy stor-
age in periods when solar energy is not available. Solar en-
ergy is being used in two major areas: for Sp/ace heating and
,1/''cooling and for generation of electricity. The necessary re-
search and development for using solar ( ergylor space heat-.
ing and cooling is well advanced. However; some' additional \-
'work is required before there can be-widesplad use of solar
. energy for generating electricity. 'It has been estimated Il
that solar'energy has the potential of supplying one-half ofI
.
the world's energy d.s.nee . I
Page 48/CH-09./(33.
(--
1
RY
The major solid fillecoal, but since
Virohmental problems -associated with Orrning
of coal, conversion projects to convert coal
t
)
there are en-
large quantities
to usable gases
or liquids are being investigated.' Coal is the major fossil
fuej resource in, the United States. It has been,, e'stimat'ed,
that a S00 -year supply of coal is availableNatural gas is
almost a perfect
content- per -unit
fortunately, the
fuel; it burns cleanly, has a high energy
weight, and can be transported easily. Un-
supply of methane is decreasing. Coal gas,
natuiol gas, bottled gas, and acetylene are important gapods
fuels. PetroleuM'is the major liquid fuel, supplying gas:
gasoline, oil, diesel apd jet fuels, as- well as being the
starting aterial for the synthesis of numerous organ it com-
pounds. The,niajQr role of the refinery is oo separate the
fractions of petroleUM and to increase the yi d of gasoline
for Use dn 4ransportation. The yield of gasol is improved
by catalytic cracking, reforming, polymerization, dehydr
nation, and alkylation, Aliternate energy sources,are NOng
developed in order to move away from the dependence upon'Vhetiti
sil .fuels that eventually will be depleted. These ali1%,-.
nate sources of energy include methanol, ethanol, hydrogen,
biomass, solar, nuclear, wind, tidal power, hydroelectric,
and geothermal. Currently, these sources of energy cannot
compete with the fossil'fuels;,Aereforel their development
hasbeen slow. However, as prices_of. fossil fuels increase,
,it is expected that most of,these alternate sources of energy
will be utilized 'tOrsome extent in supplying the world's en:
ergy needs.
While energy production is.important, perhaps as much
stress should be placecrupon energy conservation. Energy
164 CH-09/Page 4.
s #
Y.
"5 a
4'4-74
\. /I
conserved is energy that does not have to be produced. The
days of inexpensive energy are gone, and energy conscious-
ness must be instilled in everyone. A number of studies
have indicated that a 30% reduction-in energy consumption
'could be achieved without_ undue haidship on anyone. Designs
of equipment, appliances, and-dwellings everything that
consumes energy should be developed with an effort to
edtce energy consumption: ,
o
p.
3>
1
Page 50/CH-09 ,
3
16 :5
I
1. Name the following compounds:
a.
CH3
CH3 CH2 C CH3
CH3
Br
b.. CH3 C CH2 CH2 CH3
H
CI
c. CH3 CH2 C CH3
Cl
EXERCISES
2.' Draw the structural formulas of the.follol ng compoundS:
a. 2,2f3-Trimethylpentane.%
. b. 1,3-Dibromopropane.
c. 1-Bromo,3-methyrbutane.
d. 2-Chloropropane.
10,
166 CH-09/Page 51
LABORATORY MATERIALS
Laboratory 1
50 ml round-bottom
distilling flask
Water condenser
Adapter
Thermometer
Clamp
Burner
50 ml Erlenmeyer flask
Rubber tubing
Boileezers
Long stem funnel
25 ml graduated cylinder c
Fractionating column
Refractometer'
Laboratory 2
Test tubes
. Glass tubing.
Ring stand
Clamp -
Burnet
Wood (splinteri or excelsior)
Soft coal:,,
Litmus paper
'LABORATORY PROCEDURES
I fs
.LA ORATORY 1. NFRACTIONAL-DISTILLATIU.
'Distillation is widely used in laboratories and th.e
chemical process industry to separate liquids that are solu-,
ble in each other. Consider a mixture bf ethanol and -water
whiCh are totally miscible. Ethanol boils at approximately,
78.5°C; water boils at 100°C, When placed in a distillation
flask and heated to the boiling point (which would.be a'
point somewhere- 78.5°C and 100°C, depending upon
the composition of the mixture), the first portion of vapor
coming off and being condensed 411d be richer in et nol
than in water. If the fitsi distillate were then re istidled,
Page 52/CH-09
44-a s
167 lt
the initial vapor would be even more rich in ethanol. And,
if this, process were repeated often enough, pure ethanol
would ultimatelybe produced. However, rather than conduct-
ing the distillation by this rather laborious process, a
fractionating column is used. A fractionating column is
a glass.column that is' packed with some inert material
such as glass heads, glass helices, or clay chips that
provides a large surface upon,which the vapor can condenses
The hot vapor rises through the packed column until it reaches
a cool enough portion of the column to condense. The liquid
then flows downward until it becomes hot enough to be re-s.
converted to vapor. Each time the condensate vaporizes,
the vapor is richer in the ethanol [or lower boiling point
liquid). In this process, called fractional distillation,
the' components, or fractionfl:of the original mixture are
separated. In this experithpnt,,,a mixture of ethanol and
water is separated by fractional distillation. All data
should be retarded in Data Table.
A'synthetic mixture of ethanol and water may be dis-
tilled, or beer may be distilled. Alternately, a mixture
Of methanol and er may be distilled.
.14
PROCEDURE.
. 1. Set up the apparatus for distillation ss illustrated,
in Figure.1. the distillation vessel is a round-bottom
distillation flask thavi6 fitted with an adaptor'
containing a thermometer. The tip of .the thermometer
should be near the point where the vapor leaves t1-1
side arm of the, distillation flask. A water - cooled
condenser is fitted to the side arm of the distillation
168 CH-09/Page 53NO110
o
..
L
i
s
o
,
t
1
t,=1
1
THERMOMETER INEOPHENE ADAPTER
I'CONDENSER
CONNECTING ADAPTERRECEIVING ADAPTER
---31. TO DRYING ITUBE IF NECESSARY
FRACTIONATING COLUMN
. RECEIVING FLASK C
i - SUPPORT CLAMPS
!) I
DISTILLATION FLASK IBOILING STONES
I
Iflask. A condenser adapter leads the condensate into
Figure 1. Basic Apparatus for Fractional Distillation.
a receiving flask. The apparatus is positioned so
that the distillation flask can readily be heated.
With.extremeTy flammable liquids, an open flame from
the burner must not be used; instead, a heating mantle Ishould be utilized in these cases. The lower end of
the, water condenser is connected to the water line,
and the upper end- is connected to the drain.
2. Mix 15 ml of water with 15 ml of ethanol and place
Ithe 30 ml of mixture in the distilling flask.
3. Add several Boileezers and insert the cork containing
the thermometer. :. I
4.: Use a 24 ml graduated cylinder to collect the distillate.0 *'
i1Page 54/CH -09
. . 169It,
t
S. Heat the mixture until it boils and record the tempera-
ture at which the first dtop of distillate appears
in the graduated cylinder.
6. Adjust the heating rate so that 'the distillateslowly into the graduated cylinder.
7. Record they temperature every 2 ml as the distillation
Rroceeds.
8. Continue the' distillation until the temperatureaches
99°-100°C. (If the. distillation resulted in a complete
separation, this point would'be after /5 ml of ethanol
was collected, leaving 15 ml of water. This ideal
separation can allhost be achieved by using a packed
fractionating column.) Record the m-voume of. residual
liquid in'the distilling flask and the volUme collected.
Plot the distillation curve (that is, _plot temperature
versus milliliters of distillate).
NOTE: A refractometer is often used to determine ,the
composition of the components of a distillation. The
refractive index of ethanol is 1.36048 at 20°C, whereas
the refractive index of water is 1.33299 at 20 °C.. ,
LABORATORY 2. DESTRUCTIVE DISTILLATION, OF WOOD AND COAL.
Destructive distillation is used industrially to pro-
duce,gaseous fuels and aromatic hydrocarbons from wood and
coal. These distillation processes will be illustrated
in the experiment.
170 CH -09 /Page 55
44
DESTRUCTIVE DISTILLATION OF WOOD
1. Arrange.the apparatus as shown in Figure 2. The short
exit tube should-be glass tubing that has been drawn
out into a capillary and cut off. The lower end of
the 'delivery tube should be half an inch from the bot-
tomof the condensing tube.
Figure 2. Apparatus forDestructive Distillation.
2. Fill the top test tube with wood splinters or excelsior,
and connect the test tube.
3. Gently heat the wood at first; then heat it strongly
until no fuTther change is observed. DeScribe the
appearance of the _volatile matter coming from the
wood. k
4. While heating, bring the flame totthe end of'the capil-
. lary tube. Does the gas being emitted burn?
Page 56/CH-09
t
171
O
5. Allow the apparatus to cool a examine the residue
in the test tube. What is the substance in the test
tube?
6. Describe the appearance of the substance in the con-.
densing tube. Can distinct layers be keen?
17. Test the liquid in the condensing tube with litmus
paper. Is the substance acidic or basic?
This substance is a complex mixture containing wood
alcohol (methyl alcohol), acetic acid, acetone,. and
other organic substances, including aromatic compounds.
The destructive distillation of wood produces charcoal,
methane gas, and liquid organic chemicals.
DESTRUCTIVE DISTILLATION OF COAL
I1. Fill a test'tube half full with finelycrushed soft
.coal. Replace the condenser (used above) with a clean
1one.
.
2 Heat the test tube containing the coal gently at
1
first and then strongly. Describe the volatile mate-
rial. Is it the same as obtained from wood?
$
3. Bring a flate to the end of the capillary tube. Is the-
gas combustible?
. 4. Heat the coal until gas is no longer given off.
5. Alloy the test. tube to cool, and examine the residue.
Describe the residue. How does it compare to the
original cost? (The residue is called coke.)-lc
6. Examine the condensing tube'and describe its contents.
I
,-
of coal.
a.
b.
c.
1
of the destructive distillation
..
Page 58/CH-09
i
4
173
./
ft
41.
. DATA TABLE,
DATA TABLE. FRACTIONAL DISTILLATION.
Distillation of Water-Ethanol Mixture
,
Volume Collected
,
Temperature °C
First drop.
2 ml
4 ml.
. 6 ml __-8 ml
10 ml. .
.
12 ml
14 ml
16 ml
.
i
/
.
Volume c.ollected: . ml
Residual volume:,_ ml
1
174CH -'09 /Page 59
REFERENCES )st
Fieser, .L.F2and Fieser, M. Introduction-to/Organic Chemistry.
Boston: D. C. Hea4. th and Co., 1957.
Griffin, Jr Rodger W. Modern Organic Chemistry.
McGraw ill Book Co 1969..1.,
Morrison, R.T. and Boyd, R.N. Organic Chemistry. Boston:...
Allyn and Bacon, Inc., 1966.
Nelson, T.W. "The Origin of Petroleum." Journal of Chemical
Education 31, 399 (1954).
Rossini, F.D. "Hydrocarbons in Petroleum." Journal of
. Chemical Education 37, 554 (1960) . ...,
Smith, L.O., Jr., and Criston, S.J. Organilc Chemistry.
New York: Reinhold Publishing Co., 1966.#
Wertheim, E. Organic Chemistry. New York:, McGraw-Hill .
New York:
...i.
Book Co., 1951.
Yohe, G.R. "Coal." Chemistry 40 (January 1967).k..
Zim erman, Henry and Zimmerman, Isaak. Element of Organic c
emistry. Encino, CA: Glencoe Press, 1977.
A
Page 60/CH-09 175 if
ik
t.
411
GLOSSARY
Aliphatic compounds: Straight-chain compouhds.
.
Alkanes: A series of hydrocarbons containing single bonds.
Alkenes: A'series of hydrocarbons containing double bonds.
lakylation: Combination of branched alkanes to form longer-chain compounds.
Aromatic compounds: Compounds containing 'the six-membercarbon ring.
Biomass: A renewable, carbon source from plantsgrasses, or water plants.
such as trees,
Catalytic cracking: A process in which long-chain hydro-carbons are broken down into two or more smaller mole-cules.
Cycloalkanes: A serie's of ring compounds.
Dehydrogenation: The removal of hydrogen from saturatedhydrocarbons to form unsaturated hydrocarbons.
,reon: The trade name of polyfluorinated hydrocarb ns used
refrigerants,.
Fractional distillation: A. process consisting of he ting amixture to vaporize and separate it into fractionsaccording oto boiling points.
0,00
Fuel.: Any combustible substance that is burned to produceuseful heat.
Gasohol: A blend of gasoline-ethanol containing 10% ethanol:
Hydrogen economy: The concept'in which conventional fuelswould be replaced by hydrogen.
Compounds having the same composition and molecularweigirt, but different atomic arrangements.
Octane number: A rating used to indicate a gasoline's ten`dency tb'knock in an engine.
'CH-09/Page 61
r
Organic chemistry: The study of carbon-containing,compounds.
Polymerization: The combination of small-chain hydrocarbons'into longer-chain compounds.
Reforming: A process inowhich a straight-chain hydrocarbonis converted into a branched hydrocarbon.
Straight-run gasoline: Gasoline obtained from the fractionaldistillation of petroleum.
Substituted hydrocarbons: Hydrocarbons in which at least onehydrogen atom has been replaced by a functional group.
Page', 62/CH-09
ti
,
7.
"MODULE CH=10
.,,3-PLASTICS:ADHESIVE. Si,AND _LUBRICANTS
INTRODUCTION
-
Plastics, lubricants,,and adhesives are-important mate-
. rials used in the energy field and in everyday life. ,,Inow.ing
the properties'of theseMateriils can assist the_energy tech-,
nfcian in making wise choices as to their utiization-as they-4
are encountered on the job.
Plastics are synthetic materials-that consist of-giantt
moi.ecules. -Several types of plastics are availablt, each
'made from different chemical starting materials. 'It is
almost impOssible to go through a day without using objects
made, from plastics- since they are used, in applications such
as packaging",-trtansportation; electi-onics, construction,'
furniture, atliing, dndapplialices- -Examples include-paints
made from plastics (polymerS,,flooring materials, synthetic
fibers. for suits, 'plastic pipes and fittings,'automobile =
steering whee,ls, telephones, dishes, combs,.and seat covers.
Plastics are frequently' used because of their excellent in-
.,,sulation properties (heat and electrical), resistance to
,..corragidri and chemicals, lightness of,. eight,- strength;
4a of colcrr;:and ease of processing. One of the maj.0 disadvan-
J.
tage4Of plastics'' they, deteriorate at hightempera,
Lures,pt in the .presence of sunlight . r- .
:life plastics,industry is'7'a multibillion -dollar 'business....
..,- It produces articleTnOt dreamed of ?everal,yeafs-ago..
...
For eAample, the Obes made 'for walking on the' moon are :maae.,,
1p
.
.1:- from flexiblelasticHsifAcone because it provides good ther-- .0 -
,
, maltInstlation thatNgthSvandsex,treMelygoold and hot temper -.'fp
. ature.s wittiput.meltik cq:.-becoming.brftell. The' use pf plas.. s, . .
.i.ics.in.the automobile industry has also increased in die'. k-. ..
= last' feN-yeafs. However, .plastics are made from chemicals-
AerVed from,petroleum a. fa, Ct. -that- somew
ha1
t, places,the.fu-
ture'of doubt.A fi ' .41 .-.
s : A. l ,
''. 'S,, ,, "e . '.
"1:: . k
. .IO * 0 .4 <7! 4
. e .CH-10/Page 1...,
179,_ ,., 0
.
Adhesives, which consist of large, syntheiismolecules
that are similar to and sometimes' identici'l to plastics,
are_used for joining many types of materials. They,are
widely used in the automobile, aircraft, electrical, aero-
space, and building industries.
Lubricants are used to reduce the friction that wastes1
energy and that tends to destroy rubbing surfaces. Primarily,
lubricants are made from petroleum although synthetic lu-
bricants-
are becoming more popular. Several factors impor-
tant in the_t.ractice of-lubrication are considered in this
module,t;!
PREREQUISITES
The student should have'completed Modules CH-01 throUgh
.CH-OS of Chemistry for Energy Technology I and Modules CH -06 :'
through CH-09 of Chemistry for Energy Technology II.
OBJECTIVES
Upon-completion Of this module, the student should be
able to:
1. Definelthe following terms:
Monomer..
Polymer.
Copolymer..
Thermoplastic.
Thermosetting plastic.
.f.-1.1.Engineering plastics .
Adhesive;
180
.4
(
4.
h. Lubricant.
Frictian.
j. Stabilizer.
k. Plasticizer.
1. Glass transition.
2. ;Identify a common- use ofthe.fbllowing polymers:
a. POlyethyl.one.
b. Polyvinyl chloride.4
c. Polystyrene.'.
d. Tefion.
e, Polymethyl methacrylate.
3. List three advantages of plastics as compared to ffletals:
4. List three limitations of plastics:
5. List four, methods of processing plastics.
6. List three%advantages of joining materials-wtth
adhesives'as compared to using mechanical methods..
7. .List three environmental conditions that play an
important role in the practice of lubricatiOn.
a
4.
;--O
CH -10 /Page 3
4
a.
SUBJECT MATTEF1.
PLASTICS
* t
The starting material for all, plastics is the monomer.
The term "monomer" is derived from :riliono," (mean-big one) and
"mer,l' (meaning unit, or pare). ponomer, theiefore,tmean
one unit or part. InAproducinglitlastics°, or polymers (Mean- °
ing many units), the small, monomer molecules/are linked
through chemical, reaction to form lOng-chain,compounds. One
of the more simple monomers's ethylene, C2HL,'".
6
H H
I I .
is C. CI I
H H
Ethylene monomer
,,
Afik
.$14
.The double bond in ethylenecan iSb rearranged as follows:
I
.Th free bonds on the end of ethylene can them combine-4ith
of ier ethylene. units to' form a sang chain, as follows:..
G
4
HHHHHHHH\-C.- C- C- C-1114111'iH.eH H HRH H H Hi
n
182
4
CH-10/Page S
I'
I
The "n" in the lower right-hand corner represents; a large
.number, such as 1000. It is common for polymers to have
molecular weights front 10,000 to 100,000. Ethylene, a gas,combines in the ploymerization process to-fOrm the solid
poiyMer called polyethylene.,
If a pure monomer A, such 'as ethylene, is polyMerized,
the polymer obtained isocalled a. homopolymer (meaning alike
,throughout):
AAAAAAA A A
Likewise, the pure monomer B can be polymerized to form ahomopolymer:
BBBBBBBB B.,But%if both monomers, A and B, are.added'to each other, and
the mixture is polymerized, a polymer called a.copolymer-i's x4
'formedL:
-- A B B A A B B.A A - A
A A ABA A AB A'A'B A
In many copolymers, the order of the units is randore(as._
.
indicated in the three preceding structures); and the prop-
erties of the copolymer are deti-mined by the katio of the
amount of Ato the amount of B in the copolymer. The prop-
erties of-a-cppolymer.are different from those of the pure
ol);mers, and copolymers can4be taildr-made tp hate proper-
ties that arp superior to tAose of pure polymers.
Page 6/CH-10-
so-
POLYMER ADDITIVESt
Most plastics used today undergo some type of modifica-
tiofi through the addition of additives. Plasticizers are
added to plastics to make them' more flexible. For example,
polyethylene and polypropylene are too stiff for most appli-
cations. However, with the addition of suitable plaSticizers,
these plastics become flexible enough to be useful. Fpr plas-
tics thartyill be exposed to sunlight; the addition of a sta-
bilizerwill prevent the bonds from being broken by ultravi-
olet rays of the sun. The addition of approximately 0.1% (by
weight) is enough to protect most plastics from decay due to
sunlight. A variety of fillers is added during the process-
ing of plastics to give,the plastic various physical proper-
ties, .one of which is to increase the plastic's resistance to
heat Accelerato-rs or inhibitors are added to'control the
rate of cure of plastics. In addition, pigment or dyes can
be,added to polymeis to give the finished product a desirable
color.
piast cs,have several desirable characteristics, includ-.
ing the4 following:
Chemical resistance 7 Some plastics are res).stant to
stronacids7 alkalis, and solvents...4
and weather resistance rlastics do not
oxidize rea ly,and, therefche, maintain theiT use-_
fulness. in'a.viriety of environments that are detri-
'mental to eals,
S.
Color 'Pla'stics can be Produced in many colors The
color is a permanedt part of the plastic, not just a
surface coating.
CH-10111de 7
184. ,
. sP
Shape Plastics can be economically formed into
many shapes through molding, machining, or extrusion.
Insulation Plastics are good insulators for heat
and electricity.
Lightness Plastics weigh about one-half the weight
of aluminum and one -sixth the weight of steel.
Strength, hardness', flexibility Plastics offer a
number of meofianicaI advantages over other materials,
especially in regard to their strength-to-weight ratio.
Plastics can be-divided into two groups on the basis of ho
they react when exposed to heat: thermoplastics and thermo
setting plastics. Thermoplastics will soften 'and flow when
heated; when'cooled, they harden. However, this process is
reversible, and the material can be melted and solidified a
number of times without change. In contrast', thermosetting
/Plastics do not soften when heated.. They form a set of
interldicking bonds between the polymer chains. Under exten
sive eating, thermosettingylastics will char and degrade
ra her than soften.',,
\\.t
'PROCESSING OF' PLASTICS
Many different processes are used in changing plasiic
granules,owders, and liquids into filial prolUcts. Thermo-
plastic materials are,suitable for certainprocesses, where-.
as, in most.cases, thermosetting materials will require other
methodssof forming. Thermoplarics are usually melted and
-reshaped before they are cooled into the final shape. Ther-
mosets are usually :Polymerized by heat, pressure, or a
Page' 8/GH-10. 185
ai s
1b
k
Z
ge
catalyst during the prScessing step. Several of the more
common processing techniques will be. considered in the fol-
lowing paragraphs. .
In injection molding of thermoplastic, 'the material in
pellet.'Or powder form is heated until it'reaches a' molten
'siate.._,Then, under hydraulic pressure, the material is
pushed through a nozzles to fill a mol.elcavity.. The material
is thencooled in the mold where it takes its final shape.
Blow molding is used to mold hollow thermoplastic parts,
such as plastic milk bottles. Air, under pressure, is fed
)41to the center of the mold, inflating the material and forc-
ing it against the mold cavity walls. In principle, the pro-
cess is similar to glassblowing.
Im-extrusion, the molten plastic is forced through a die
that is shaped to the desired form. This method is, used to
make rods, film; tubes, and pipes. .The final form is Cooled
by air or water and is then cut to length.
Calendering is a process used to produce sheets or
films. The heated plastic passes through a series of Aeated
rollers to obtain a,uniform thickness. The material then
passes between chilled rollers to take its final set.
ast,ing is primarily used for therdoset materials, No
pressure is used in this process. As a liquid, the material
is poured into a. mold cavi,ty. After the mold is filled, the'
material is cured into itsfinal hard form by using room tem-.
perature or by using heat.
Sheets of cloth, glass, or paper can.be impregnated with
plastic resin by the manufacturer and then laid on top of
each other to form a desired thiCkness.. These "laminates"
are then cured under pressure to form a strong material.
Circuit boards for electrical devices are constructed in a
similar manna, as wel as man other products such as tahle
186CH-10/Tage 9
tops, wallboards, and rods. Glass fibers are effective ina
strengthening polyesters or epoxies to form fiberglass.
Boats are an example of the structural uses of fiberglass.
PROPERTIES OF MAJOR PLASTICS
The following.paragraphs)contain descriptions 9f several
physical and chemical properties of major plastics.
A) major family of polymers is known as the polyolefins.
An olefin is a compound in the ethylene family; that is, it
contains double bonds. Polyethylene is the major member of
this family. Polyethylene is made in two -ranges of density:
low density and high density. Low density polyethylene has
a relatively short-chain molecular structure; whereas 1;411i
density polyethylene has a much longer chain structure. Low
density polyethylene is used where flexibility is a primafy
consideration, whereas high density polyethylene is used in
applications requiring more strength, such as bleach aattles.
Polyethylene is used for containers, toys; freezer bags,'
houseware items, detergent_bottles,'and wire and cable inSu-
lation.
Another member of the polyolefin pol propylene,'
is made from prop lene gas, which is obtained from tro-
leum industry.' T e s-trudture of polypropylene ,is given by.
the fallowing:
H H H H' H H
I I. I I: I -- Is-CCCCC-C-I I I -1 I
CH3 CH3 CH3 CH3 CH3 CH3
Page 10/CH-10
n
Polypropylene
9
41.
11-
Although polypropylene is more costly thadpolyethylene, it.
has better rigidity', temper ture stability, ,crack resistanc,.
and tensile strength. Polyp opylene is used in pump hous:-
ings, electronic pFts, indutrial packaging, luggage, aftd
housewares. In adilition, it is widely used in the construe;
tion of hospital equipment because of its resistance to them-
iCals, its transparency, and its ability to be .sterilized.
Vinyl resins cover a broad family of plasticg; which
range,from hard, rigid materials to soft, flexible products.
They 411 have the vinyl radical in their structure:
H
C1 1
=C1
H 4l
Vinyl radical
Various side groups can'te added to give polymers.of varying
properties. The most common vinyl resin is'polyvihyl
ride (PVC). Its structure is shown below:
H H. H H. H H H
1_ 1 1 1 1 I I.CC C CCCCC1 I I I 1 1. 1 1
H Cl H Cl .H Cl H ClIlm n
Polyvinyl dkloride
As shown, chldrine (C1).s.as the atom that is attached to'.
the vinyl radical. Vinyl chloride is polymerized by the'.0,
breaking of the d9uble bond and..the'recombination of the
molecules to form a icing chain. The vinyls have good.
strength, excellent water and chemical, resistance, and many
color possibilities.
188.-,
e.0
0 1
I
CH -10 /Page' 11
A unique.iCharacteristic_of PVC is its'self-extinguish-
ing property. F exible PVC is used for tubing,.wire coat-.
ing, gaskets, a heeting. Rigid PVC is used for pipe,.
siding, chemical. storage tanks, and gutters. Sheet PVC is
used for shower curtains, raincoats, and automo ile seat0 S
covers: Another tuber of the vinyl family of esihT, poly-.
vinyl acetate, used primarily as an adhesive for wood,
paper, cloth, nd leather. Polyvinylidene chlo ide is Sim-
1 ar o p Cept that it has two chlorine
atoms on the carboh atom instead- of 4e, as -in-PVC:7
H Cl Cl H Cl H Cl
I 1 I I I I
-C C C C C -C -CI 1.1..1
H Cl H Cl H Cl Hn
Polyvinylidene chloride
With characteristics such as being odorless, tasieless,..
tough, and having low water transmission, polyvinylidene is-_
extensively used as'a food wrapping mateitial. It has the ,
trade name of Saran. Since it is resiStaht to moisture and
weathering and__is sufficient in strength, polyvinylidene
chloride' is frequently used as webbing material -for outdoor,
furniture:
Styrene resins are usually considered:as a separate
family of resins because they are quite different from the
vinyl resins. However,as can be seen from their structure,
they are actually-vinyl..resins, with .a benzene ring being
the group attache&to the vinyl radical!
e.
- .
h.
Page 12/CH-10,
r
S'ki
:Cs It
, *tt,.
H H H
1 I.C C. C C C C
1 I 1 . ,
Polystyrene
Polystyrene products are found almost everywhere because of
the low cost and ease'of processing the plastic. Polygtyrene
is used for many disposable products; such as picnic utensils
and food containers. Other uses include the following:
picnic coolers; model a'irplaaeand car kits; l*Isewates;
'appliance housings (such as forradios, television, mixers,
and refrigerators); and interior automobile parts. Perhaps
the most commonly known application isthe white plastic
coffee cup.
Three monomers. .icrylonitrile, butadiene, and styrene- ;
can be/combined to produce the plastic ABS.; ABS is hard
and to a combination that is uncommon in thermoplastics.
ABS polymers are used in housings of various types where
rigidity, strength, andsa glo-S-sysurface_are important. .ABS._
`,plastics can be electroplated to give thefiJIiiiesiPi.6add-t
a metallic ippearance. Electroplated ABS' is used--in auto-
motive,' 'appliance, hardware, and-houseware applications.
ABS is-also used in gulf club heads, illUstrating the
strength of this styrene polymer., Styrene-butadiene
a-related polymer, isthe primary synthetic rubber in
use today._.
f. , Most of..:*triembers of the polyester family are ther-
mosetting" plaitics.. However,'-polycarbonlke'resins are ther-.
. .
moplas-tics. This. fsolyester contains the ester group with
1,9.0CH-10/Page 3
.
e.
O
.>
J
benzene rings attached., Polycarbonate resins are in a group
of plastics called engineering pla6tic* a term used to indi-
cate that the piasilbaas.Outstanding,mechanical-,
and chemical characteristics. The dimensional stability of
`polycarbonates allows them to be used in
components where close tolerances are requir . Application's'
of polycarbonates include sunglass lenses; shop heels, coffee
pots, football helmets, pump impellers, cooling,fans, and,
structural-housings fur-/Tower-,tosIs-;--
There are fiVe main cellulosic polymers: cellulosJe ace=
ate; cellulose nitrate, cellulose propionate, cellulose ace-
ate butyrate; and ethyl cellulose. These ce;lulose,plistics
are,made from cellulos,e, which is obtained from wood pulp. or,
cotton, inters. The natural cellulose is chemically modified
to produce_the plastics. Cellulose nitrate was the first
commercially produced plastic - in the year 1868. It was
widely used in producing film for the movie industry. A'Unfor-.
tunately, ,the flamm'abilitysof cellulose nitrate was
cause ofmany fires in movie theater*: Cellulose's limited ,
,applications, include the following: indastrial.products,
shoe heels, and housewares. Naturally, its use is 'curtailed40K- ,
.
because of its high flammability. Cellulose acetate' has ,good
mechanical and electtical-(insulating) properties. It is
used in making-to csafety goggles, tool handles, combs,
''cutlery'handles,' knobs, and housifig-stforsiall electrical
appliances. BecauSe of its ease/of processing, its hardenS,
and 4s stiffness, cellulose Tropionate'is used in toothbrush
Ihandles,pen'and pencil barrels, steering wheels, screwdriver-.
handles, eyeglass .frames, and,telephone'housings. thyl
is used. in flashiight.cases, furniture, lugg e,,and
App ations Sf c'ellulose aceiate,butyra e iicl de,
Page 14/0-17,10
1ft
jsafety glasses, outdoor advertising signs, and structura1A-
panels in buildings. .
Acrylics are methyl, methaorylafe polymers. The outstand-
inging properties of acrylic plastics are exceptiionalclarity
kncrlight transmission, coldrabilkty, and weather resistance.
Acrylics are sold under the trade names of Lucite atdPlexi--
glas Acrylic sheets are used as windows, instrument panels,
illuminated sign's, lighting fixtures, and so forth - wherever
a glaSs-like material is needed. .In the form of fibers, the. ------.
acrylics are, used atPcarpets.e'The two main classes of polyamides 7- that is, compounds
that con alri NH or NH2 groups include the following: ,4,
-nylon's and versamids. .Versamids.are.primarIly tised,as',"thot
melt" adhesives in applications uch as bonding shoe soles,
ris'lino the upper shoe. These' ad I iVes are moisture resistant
and'flexible, making them ideal for footware applic'ations.
A number of nylons are produced - the most common being
Nylon 6,6:
H H.
, 1 .H
0
(CH2) 6 '1\,1
.
Y n
A
,Nylon 66
ce
r
Characterisy.c's that bake nylons valuable-include high heat,
chemical resistance, outstanding toughness, and ilexuial
small indi'llstrial parts ai-iiidde-df-tYlgn'than of.afiy Vther
hingeS.;-combslishiN_lines,'bealigigs,* and rollers. Mdre
4
is used in,
-'-strength. Nylon
II: plastic. Long,wearing.gears made 4 nylgn are quiet-running
A and never require; 1.ubrication..
102
'4,
o I
.0-1b/Page ;It.
4
Polyphenylene oxide (PPO), developed by General Elec-.
tric, new plastic. It is increasingly being
used as engineering plastic because of its excellent elec-
trical properties. Polyphenylene oxide is used in battery
cases, electrical housings, switches; capacitors, and printed
eHr* circuits. Because it can withstand-prolonged exposure to hot
water, it is also used for plumbing parts and food processing..
'equipment that must be / sterilized.
:Acetal resins are made by the polymerization of formal-
dehyde to form a structure with alternating carbon and oxygen
bonds:
H
0C-0--C 0C-H n
Acetal resin
Acet1 resins are rigid thermoplastics that can be used to
:mike parts that are substitutes for metal articles. The
1 °resins have excellent abrasion resistance, and, many times,
they ,outlast comparable metal parts. Acetal plastics can
be electroplated to form metal-like products. Acetal is
used'in carburetor patts., bushings, gearsand fan blades.
Jan blades, such as those used for cooling movie projectors,
are almost exclusively made from acetal resins.
Polyurethanes'(aiso called isocyanates) are used as
foams, coatings, and rubber substitutes% . The major use of
polyurethanes is in the production if flexible and rigid
...foams. The two components of polyurethane foam are mixed
just pri6to foam formation in molds, or they.are foamed-.
in-place4usually-fo-r:ins-ulation applications) . The foamo
is used for flotation in cavity filling of boats, pontoons,
Page 16/CH-10
193P
and life jackets. Urethanes- are gaining popularity in energy-
efficient.home and building construction as a barrier to out-
side air along baseplates, windows, andblectTical entrances
to the structure.
TetrafluorOethylene resins. (TFE) are extremely temperd'-
ture.otable. As shown in the structure below, the carbon
chain is completely protected by fluorine atoms, thus account-
ing for the temperature stability of these compounds:
F F F F F F F
1 I I I I I I
C C C C- -C C CI I I I I I IFFFFFFF n
4
Tetrafluoroethylene
The trade name for thee fluorocarbon polymers is Teflon.
Teflon is the most chemically inert of all plastics, resist-
ing attack by chemicals even at elevated temperatures. Tef,
ion's coefficipnt of friction is the lowest for any known
solid material; therefore, Teflon is used as a solid lubri-
dantiin bearirigs and bushings of industrial machinety. One
common application of'these plastics is, in the'manufacture
of non-stick cookware. Teflon canbe used in the range of
-450°F to 550°F. Because of its excellent insulating prop-
erties,'Teflon is used to coat electrical wires.
The most common thermosetting plastics in use are the
phenol formaldehyde resins called phenolics. Characteris
tics of phenolics that make them so valuable include the .
following: relatively lOw cost, excellent insulating prop-'
erties, inertness to most solvents, heat resistance to
500°F, and dimensional stability. Large quantities cifPhe7---
nolic adhesive are used in bonding plywood. To impart
t
194
CH-10/Page 17
r'
4
4
-dr
special characteristics, fillers are often used in phenolics.
Fillers that are commonly used include graphite, asbestos,
wood flour, and glass fiber.
j Polyester resins are combined with glass mat or chopped
glass fibers to form the product known as fiberglass. These
resins are used to produce boat hulls, automobile body com-
ponents, air,craft body components, hammer handles, 'automotive
gears, and distributor cap's. Polyesters have good weathering
characteristics and are strong and tough.
Melamine formaldehyde plastics are thermosetting com-
pounds that are hard, scratch-resistant, and almost unbreak-
able. Because melamine retains bright colors, and resists
oils, .fats, and detergents, it is used to make dinnerware,
coffee makers, kitchen' counters, and tabletops.
Inasmuch as epoxy resins are versatile, they are used
for coatings, adhesives, laminates, molding parts, and en-
capsulation-by potting. The structure of the epoxy polymer
is shown as follows:
CH3
0
CH3
CH2 CHCH2
OH
Epoxy resin
Epoxy adhesives are strong and can be used to bond metals,
glass, ceramics, and dissimilar materials, although.the bonds
tend to be somewhat brittle. Epoxies are used in sealers,
aircraft skins, boat bodies, printed circuit boards, insula-
tOrs, and laminated sheet materials.
The silicone materials are produced as resins, fluids,
and elastomers.. The chemical structure of as
follows:follows:
Page 18/CH-10
195
f
, CH3 CH3 CH;CH3
0-- Silicone
1
CH3. 1
CH3 CH3 CH3 n
As can be seen from the structure, the backbone of silicones
is a silicon-oxygen-silicon repeating structure. Silicon
diolc.ide (SiO2) is sand, an inert: temperature-stable sub-
stance. Therefore, silicones are shown to exhibit a remark-
able temperature stability. By replacing the methyl groups
with other radicals and by adterinethe chain length, a vari-
ety'of materials can-be made, ranging from low viscosity
fluids to semirigid solids. The solid molding compounds are
used for transfer and compress ion molding, whereas the semi-
liquids, are used for coatings and sealants. Silicone rubber
is used where temperature stability is required. It can
'stretch up to 800% and has excellent tensile strength al-
though its strength is not comparable to carbon based- rubber.
Silicones, which; can be.used at a temperature range of -150°F
to "600°F, are resistant to radiation, water, chemicals; oils,
and oxidation. In addition, silicones ar'odorless, taste-.
less, and nontoxic" RTV (root temperature vulCanizing) sili-
cones are available in "squeeze'? tubes for use *in Sealing and
adhesive bonding. Silicone liquid is used as a mold release,,
or a parting compound, toallOw finished parts to be readily
d,from molds. .
CH -l0 /Page 19
ANALYSIS AND TESTING OFPLASTICS
Testing,and analysis of plastics can be a complex
operation that requires sophisticated equipment. Positive
identification is often accomplished by using infrared
spectroscopy. However, rather simple tests are often suf-
ficient to identify plastics.--,the most common being the
burning ;est, or flame test. The first. step in the identi:
fication of a plastic is to deterMine If, the plastic is a
thermoplastic or a therioset. A small piece of the plastic
is placed in a test tube and i&f heated. If the plastic
. melts, it is a thermoplastic; if the plastic-chars and de'-
-..composes, it is a thermoset. Next, a strip of the plastic
is burned., The flammability, color of the flame, presence
or absence of Smoke, aid odor are observed! Very ofteli the
plastic can be identified by: comparing the observed prop.er-
, j ties with those listed in a plastics flame-test chart. It
is also helpful to have a series of known plastics to com-
pare to the unknown substances.
Plastics and articles made froth these plastics are. .
often subjected to a number of tests. Standard tests for
plastics have been developed by groups such as the American'
Society foi Testing Materials (ASTM). The properties tested
include physical, electrical, thermal, chemical,, and optical.
Physical or. mechanical teSt,s include tensile strength,
elongation, compreSsive strength, flexural strength, and .
cold flow. Most of these tests scan be made under ambient
conditions or under conditions of high moisture, low tem
peratuye,'or hiih.tepperature. The conditions to which the'
finished article will be exposed shouid te'simdlated to the
greatest extent possible..
Page 26/CH=10
1 9
J. .
*It
Ns.
Tensile strength can be defined as "theresistance of
a material to being pulled apart." The test is performed by
clamping a standard test specimen usually 0.125 inch xt.5
inch x 8 inch ,at both ends in the jaws of a tensile tester.
The sample-is-pulled until,it breaks, and the maximum load
that it carried is observed on a dill'or recorder. The psi
(pounds per square inch) rating pf the plastic is determined
by dividing the maximum load by.the cross-sectional area of
the test specimen. The method for tensile testing of plas-
tics is illustrated in Figure 1. Elongation is determined .
at the same time that tensile strength is obtained. Elonga-
tion is
same
distance that the specimen has stretched at the
break point.
1\3
II CompressiVe strength Is the opposite of tensile strength.
It is defined'as "a measure of the ability of a material to
.
TEST MACHINEFIXED HEAD
SPECIMEN
TEST MACHINE.MOVABLE HEAD
LOAD APPLIED
Figure 1: TenSile Test Method.
with§tand.being ,Crushed under a load." The ASTM test speci-. menfgr compressive strength is 0.5 inch.x 0.5 inch x 1 inch.
98CH-10/Page 21
1
I t
Flexural strength is defined,as."a measure of the abil-
ity of amateriat to bend or flex.1! The ASTM test method
calls for a 00 inch X.0.5 inch x,5 inch test .specimen to be
supported on two. knife edges which are four inches apart. A
third knife edge is placed centrally on the opposite side,
and - pressure is lapplied. -Then,' the flexural strength is mea-
sured at the break point. The method for determining
flexural Strength of plastics_is shown in Figure 2.
LOAD' APPLIED
4;>
OF TEST MACHINE
a
Figure 2. Flexural Test Method.
. One major disadvantage of many plastics iS their c ld
sow; therefore; the measurement of bold flow is a Comm
test. Cold flow is the difference between the original
dimensions and final dimensions. after specimen has been
loaded for a period of time and then removed. Cold flow
is important when plastic parts are mechanically fastened
(for example, with bolts and screws).
. Page 22/CW-10
.14
1 g
Dielectric strength is one of several common electrical
tests. It is a measure of the insulating capability of the .
plastic. Dielectric strength can be defined. as "the voltage
at which electrical break-down occurs."
An important property of plastics is their glass-tran-,
sition temperature. At low temperatures,' polymers exist in
the glassy state; that polymers have the properties of
glass they are hard and brittle. As the temperature of the
plastic is raised, its properties undergoa change known as
the "glass-transition." Above the Class- transition tempera-.
ture, the polymer becomes.rubbery, soft, elastic, and more
frexible. This temperature is not sharp, like the melting
point of crystal; rather, the transition occurs over a range
of temperatures,
,There are, three chemical tests normally performed on
plastics: acid, alkali, and SO-I-Tent. Both concentrated and
dilute solutions are used'in the tests., The plastic is ex-
posedto those substancii that could be encountered by the.
finished product. The plastic is then checked 'Visually for
decomposition, crting, or discoloration. Often the test
specimenfor tensile, flexural, and cdmpressi6n tests are
subjected to chemical expogure.pxior toesting to determine
the effecf of the exposure upon mechanical strength.
200CH-10/Page 23
O
ADHESIVES
There are many methods of joining materials, including
. nailing, screwing, riveting, bolting ;'soldering, brazing,_
welding, and ashesive bonding. Bonding of materials with
plastic adhesives has several advantages over mechanical
methOds. The following are examples:
. 1. Certain materials could not effectively be joined by
, any other means, Exampl4 include the gluing of ce-
ramic materials and the fastening of paper labels to
cans or bottles.
2. There is a more uniform transfer of stress from one
material to another with the use of adhesives. For
example, localized stress is minimized by using id-
hesives to join aircraft components.\ Probleins asso-
ciated with stress concentration ,and fatigue crack-
ing are common when components are joined by rivet-.
ing.
3. Corrosion of joints between dissimilar metals is
reduced by using adhesives s i\nc(e the adhesive joint
does not transfer electron's.,
. 4: Adhesives not only. bond material .together but Also
pToyide an of active seal to keep water out of com-°
ponents.'
St 'Adhesive bonding,is relatively simple, fast, and
economical.
6. Often,,considerable weight reductions are achieved `
'by using adhesives to join materials,.
-Page 24/CH-10
.1i
I
1
1
1
bisddvantages of adhesiVes_dApde the folloiving:, . f-,-
1. The Materials-foi--.jqiningmust be c4eaned and pre-.4,
pared for bonding..
2. 'Heating is sometimes required to form the bond.
, There is no uAiversal adhesive; -that is, each appli:
cation.mUst be considered independently.
4. Strengths are often directional.
5.. Full strength. is not developed immediately.,
Adhesives are widely used in the automobile, aircraft,
electrical, aerospace, and building industries. The,adhe-,.
siVes can be Classified as to use, chemical composition,
method of application, and hardening or setting method.
There are /three categbries based -upon chemical composition:
thermosetting, thermoplastic, and.elastomeric.,
Thermosetting adhesives'are converted by chemteal reac
tion into a permanently hard, rigid bond. 'Epoxies, phenolics,
polyesters, and acrylics are ali therMOSetting-adhesives that
/ find widespread use. .The more common thermoplastic resins'
include polystyrenes, polyamides, cequlosios, and polyvimyls.
Elastotheric resins are.,used primarily to modify thermosetting
adhesives to make them more flexible. Neoprenes,
polysulfides, and butyls'are the elastomertc_resins commonly
used.
Many adhesives are dissolved in a solvent = eifher.water.
or an organic solvent. The adhesive bond forms when the sol-
.vent evaporates from the bolided joint. The thermosetting,.
adhesives are normally two-part formulations., When the parts
are mixed, the chemical reaction begins and the'ond starts
", to form between the materialS being joined. Other adhesivts;
such As the hot-melt adhesives, must.be heated or melted._
When they cool, the bond is formed to join materials.I
-CH-10/Page 25
ID*
e.
Some-of,the common adhesivescare listed in Table 1.
- well as the types of materials'that are joined by the adhe-.
sives.
6
TABLE 1. ADHESIVES AND MATERIALS THEY JOIN.
' 4
:Groui). Chemical Type
,(or source) Materials Joined. , .
Animal glues.
Animal bones OT hides Paper, wood, fab-rics
Vegetable glues%
.,,Starch,
Paper and falrfc's
Natural resins
, '
Asphalts
.
Gum arabic ,
Flobr'tiles to'".' concrdte
Paper, fabrics :
Inorganiccements
Cement(Abrt'land) .
--, _
Britks, rocki.
ThermosettingresinS,
,
:_
.
4
Epoxies ,'" .
.
..
Sil,icOnes ,
....-
Urea, formaldehydes'
Polyurethane
.
Metals, glass, .
, many plastics
Silicone,rubbers;metals cseareT)
Plywbods
Paper, fabrics\
.. . .
Thermoplastic. reins.
,
,
.
A
,,. - . 1
, Polyamides -_
s.
Acrylics
Cellulose ,
. _
..,
Vinyls.
Paper, leather(hot-melt) .
Glass, acrylics
tlass, wood;paper
Wood ,
1 /
Pafe 26/CH-10 40340.
k-
Of,yr
LUBRICATION
8
.e
Tpe practice of lubrication began shortly after the
invention of the wheel and axle. When two bodies move or
rub relative to one andther there is a force that tends to.,
interfere with the motion. This force is called friction,
and substances that' are, used to reduce friction are called
lubricants. Lubrication' is important since frictionN,mittes
energy and tends to destroy the Luh4ing surfaes.
Speed, load, and temperature ,are important: consider-
,in lubrication practice. 'High speed,increases the
lubrication difficulties. Modern aircraft and power plant
turbines operate at fast speeds, and some grinding and tex
tile spindles aperlte at speeds up to 100,000 revolutions
per minute. The load on a bearing surface-is distributed
over the area of the' interface. These loads are expressed
in.pounds per square inch (psi). Loads in aerospace appli-'
cations areas high as 50,000 psi. As speed a-n.d.---load in-.
crease, the operaing temperature increases. High teMpera-
tures cause a decrease in viscosity and make it difficult to,
maintain a film of-ldbricent.
Design engineers use three basic types of frictional
components to support mechanical motion: bearings, gears,
and cylinders. The lubrication of these cotponent
tant since they are used in transportation systems, manufac-
turing plants, mines, power generating plants, and processing
plants.
In addition to speed, load, and temperature, other envi-
;Onmental conditions are often important and, therefore, must
be considered in lubrication practice. For example, in nu-_
nu-r . .
clear power plants, radiation destroyssmany hydrocarbon and `
2 0 4
CH-10/Page 27
*6e'k
synthetic lubricants, and, in spfce vehicles, the problem
of vacuum and tempera ure extremes is encountered.
Lubricants may be gaseoys, liquid, plastic, or solid.
Table 2 is a classificatiori of lubricants by'state.
TABLE 2. LUBRICANTS.
State Lubricant
Gaseous , Air, helium, carbon dioxide,
...
Liquid.
Straight oils compounded withadditives
Tallow, lard, castor oil, palmoil
Sricones, polyglycols', esters
,
i
Mineral oils-
Fixed oils
Synthetic fluids.
Plastic.
Petroleum greases, siliconegreases
.
.
Solid,
Graphite, metal i.lms,polymerfilms, molybdenUmAisulfide,other sulfides, wax, borax,mica, talc, fluoride plastic
.
A variety of additives are used in petroleum lubricants.
Inhibitors are added to preverit rust and corrosion. Other
additives depressthe pour point,'retard deterioratjon of the
lubricant, clean the metal surface (detergents), keep solid.
Page 22/CH-1.O
205
(
I
wear particles'dispersed and suspended and prevent
foaming of the oil. Polym'ethacrylate esters, and other acry-
,lates are added to 9.11 to improve their viscosity index.
They'Make the viscosity of oils less temperature '-iesponsive.
At high' loading, petroleum oils and ifeases are squeezed
out of the bearing surface, leaving the metal surfaces'in
dir9c-t contact. To preventidear and galling in such cases,
solid lubricant is used. Silver or,silver alloys may be'
electroplated on steel; they. act a high.load-carrying lubri-
cait. Teflon resin, in com4n n,with a glass fiber matrix,
has 3. low coefficient of friction, an almost cony fete
cal inertness, and is usable over a wide temperature range
from minus 450°F to plus 500%.
0'
206./,'Clir10/Page 29
0
.uo
N
So
LABORATORY MATERIALS
Laboratory 1
Castor oil
.Glycerol
Stannous octdate.
Silicone oil (Dow-Corning 202)
4-methyl-m-phenylene diisocyanate (tolylene-2,4-diisocya-
nate)
Paper cups or milk-carton
Sebacoyl, chloride (5% in carbon tetrachloride)
hexamethylene diamine (5% in wafer),,-
,
Dropper
Glass rod
Small vial (such as a litmus paper vial)
Ring stand
Clamp
Beaker, 600 ml
Test tube
Laboratory 2
Glygerol
Phthalic anhydride, powder
Beaker:50"ml
Glass stirring Tod
Watch glass
Electric hot plate
Mortar
40% formaldehyde solution (pormalin)
Test tube
Saturated aqueous solution of anil ne hydrochloride
Page 30 /CH -10
t4cite or Plexiglas pellets or chips
100 ml distilling flak
. Condenser
`Heating mantle
Theriometer
E.:43endable glass jar
Benzoyl peroxide
Aluminum foil
Hot water bath
Laboratory 3
Beaker, 150 ml
Beaker:, 400 ml
.Erlenmeyer flask, 125 ml and 250 ml
Dropper
Separatory funnpl
Ring and ring stand
-Litmus paper
Dignethyldichlorosilane
Ether
NaHCO3, saturated solution
BorixideNa2SO4, Inhydrous.
Oil bath'
Hot filati
208
0
t
CH-10/Page-31
f
LABORATORY PROCEDURES
LABORATORY 1. .POLYMERIZATION, PART I.
Polymers are giant chemical compounds formed by a'
process, called "polymerization," in which'small compounds,
called monomers, combine with each other. The molecular
weights of polymers can be in excess of 10,000 amu., In the
first,part of this experiment, a polyurethane foam is pre-
pared from castor oil and glycerol. Although polyurethanes
are not commercially made'f-rom these starting materials,
the experiment illustrates the methods used. ,Polyurethanes
can be prepared as a rigid molding material or as a flexi-
ble, rubbery-material. Most polyurethane goes into the
production of foamed plastics, which can be either rigid
or, flexible. These foaffs are good sound and energy absorb-
ers, providing good cushioning properties. These materials
are used in refrigerator insulation, sponges, automobile
and furniture cushioning, and mattresses.
In the second part of this experimeht,LNy-lan 6-10 will
be prepared from sebacoyl chloride and hexamethyl,enediamine
by a procedure called the Won Rope Trick. The experi7.
ment is often rased to illustrate polymerization reactions.
Nylon was first introduced as a fiber to weave hosiery as
a replacement for silk. Because of its high strength and
ease of 'processing, nylon hasioecome one:of the leading+-polymers of-the plastics industry. A few of its. many appli
cations include combs', drawer slide's and rollers, fishing
lines, electric tool housings, bearings, and gears.
Page 32/CH-10
r
209
r
Polyurethane
ti
1. Weigh out 35gof castor oil and 10 g of glycerol into
a wax-lined paper cup, using a V)p-loading balance.
2. Mixand add 0.5 ml (5 drops) of stannous octoate, 10
drops of silicone oil (Dow-Corning 202), and 10 drops
of water.
3; Using a glass stirring rod, mix these ingredients th9r-
oughly until a creamy, viscous product is formed.
4. In a separate container, weigh out 30 g of 4-methyl-m-
phenylene di socyanate (tolyl diisocyanate)% CAUTION:
AVOID CONTA WITH SKIN, EYES, OR CLOTHING SINCE-THE
MATERIAL CAN CAUSE SKIN IRRITATION.
5. Rapidly add all of the 4-methyl-m-phenirlene diisOcyanate.
to the mixture in Step 3.), Mix rapidly and thoroughly to
forma smooth,Iibmogeneous mixture..
When the container' beComes warm to the touch, stop stir-.
'ring and place .the containexon,a piece of newspaper in
a fume ,,hood, allowing the reaction to proceed.
7. After the foaming has stopped, allow the polymer to .cool
and "set" for\ several hours; then remove the,fo from
the cup. The foam \should be of the'compressie4
Nylon
Th
CAUTION: AVOIDS BREATHING TIE VAPOR FROM ANY OF THE REA-
GENTS USED IN THIS EXPERIME. DO NOT. ALLOW ANY OF THE REA-
GENT& TO CONTACT THE SKIN; IF THEY DO, WASH OFF IMMEDIATELY.
21 o*;
I
CH-10/Page 33
1. Pour 25 1111 of the hexamethylenediamine solution into
a beaker.'.
2. rnta a clean 150 ml beaker, add 50 ml of sebacyl chlo-
ride solution.
3. Tip the 150 ml beaker slightly and slowly add the aque-
ous hexamethylenediamine solution. Try to avoid mixing
.s the two liquids by pouring the aqueous hexamethylene
solutiok slowly so that this layer remains on trop.
4. Nate the film that forms at the interface between the
two solutions. This is the nylon polymer.
5. Reach through the upper layer and rasp the nylon in-
terface.with a hooked wire or forceps. Wrap the string
around a test tube until approximately two feet haveO
been removed. Do this by rotating the test tube.
6. Wash the nylon thoroughly in a bath of 50% acetone and
50% water;: then allow it to dry or dry,it between paper`
towels.
7. Try melting some of the nylon after it is certain that
all of the acetone has been removed'.
8. Compare the strength of fibers drawn out of the melt,
using a.wood -splint with the original string.
o 9
LABORATORY 2.. POLYMERIZATION, PART II.
Alkyd Resins /
The condensation product of polyhydroxyl alcohols and
anhydrides is a type of polyester known as alkyd resins..
These resinsgare used in makifig modern enamels and paints.
Page 34/CHVIO
211,,
Into a 50 ml beaker, place 2 g of glyerol and 3 g of
powdered phthalic anhydride.
2. Mix with a glass stirring rod.
3. 'Cover with a watch glass and heat gently over an elec-
tric hot plate. (An eleCtric hot plate is preferable
to an open flame since the resin is flammable.)
4. Continue heating until large bubbles form and the mix-'
ure puffs up.ew
5. Allow the resin to coal.
6 Grind the resin and try to find a suitable solvent.
(Try benzene, chloraform, 'and 6 N HC1.)
7. If a suitable solvent Is found, pour some of the solu--'
tion onto a piece of' metal or wood. Does the resin have
any of the desirable characteristics of a protective
. Plaint?
4
Phenolics
The ph4nol formaldehyde resins, commonly known as phe
nolics, are produced from the reaction of phenol .(carbolic0
acid) with formaldehyde in the presence of'a catalyst. These
resins; called Bakelite plastics, were some of the earliest
plastics produced..
1. Into a test tube, add 10 ml of 40% forthaldehyde solution
(called Formalin).
2. ,Into another test,tube,.add 10 ml of a saturated solu-
tion of aniline hydrochIpride in wat2r.
3. Simultaneously pour the two solutions into a 50 ml beak-
er.
4 Note .whether the reaction, gives off .heat or abSorbs
heat.
212
CH-10/PAge 35
°N\
SI
5.
4
Phenolics are hard, rigid, heat resistant materials
that are brittle.' amine the product and compare
its properties with those given previously.
I
Acrylic ReSins
The acrylic resins (methyl methacrylate polymers) have
outstanding clarity, light. transmission, weather resistance,
and colorability. They are Marketed'in the United States
under the-trade names Lucite and Plexiglas. The methyl
methacrylate polymer is made by adding benzoyl peroxide, as
an initiator, to the Monomer methyl nthacrylate. EXTREMEAtio
CAUTION MUST BE OBSERVED IN HANDLJNG BENZOYL PEROXIDE SINCE
IT, IS VERY EXPLOSIVE AND MAY BE DETONATED IF-IMPROPERLY
STORED OR HANDLED. To avoid the grinding effect such as
that obtained when.screwing_on a bottle cap., benzoyl r4rox-
id'e is Shipped and stoked in :a,paper container. ,
1. Place ,25.g of Lucite or" pelfets or chips in
a 100 ml distilling flask with ground glass cqnnectio*.s.
Attach a condenser and distill, using A heating mantle.
CAUTION:. AVOID INHALING THE VAPORS OF THE MONOMER
METHYL MkTHACRYLATE. t
3. At abbut 300°C the polymer softens and,undergoes rapid
'dePolyterizatiOn, Donning the monomer. Continue the
distillation until most of the solid has been converted
into liquid.
"4. Redistill the liquid 'and collect the distillate between
100°C and 110°C.
S. The, yield of monomer should be -about 20 g.
.Page 36/CH -10
213
1 14O
4
6. TO repolymerizp.:the mehyl methacrxlate, place 10 ml of
the liquid,in a expendable glass container (such as a
baby food jaland'add:0:01 g, to 0.02 g of benzoyl per-
oxide. CAUTION: REREADTHE'PRECAUTIONS FOR HANDLING
BENZOYL PEROXIZE GIVEN AT THE BEGINNING OF THIS EXPERI-
MENT. BE CAREFUL TO USE e.01 g, NOT 0.1 g.
7. Cover the jair with a piece of aluminum foil that is.%
held in place :140,1a rubber band.
g. Place the jar it a hot -water l*th that is kept just be-
low the boiling point of water for approximately on
half hour.
9.. Allow the pdlymer to cool; then observe its proper ies.
al
LABORATORY 3. PREPARATION OF A POLYMERIC SILICONE.
46
Silicone resins tave many diverse applications, ranging
from low viscosity 'fluids to semirigid Solids that resemble
rubber. Silicone materials can.,be used over a wide tempera-
ture range from -140°F to 60 °F. Ir adiitionto heat, they
are'resistant to ox,idation;ichemicals, and water: Silicones.
are used as protective coatings, in adheSive bonding, and in
gaskets that are fuel And solvent resistftt. '
silicones have alternating silicon and'oxygen atoms in a
straight chain, with a Variety of ide chain grdups. Va10-
tions in silicone propertAslare obtained by varying,the'llde
chain groups. 6
In this experiment; a rubber-like silicone polymer,'
/,,Commonly known as Silly Putty,- will be Made by the hydro-
lysis (reaction withiwater) of dimethyldichlorosil'ane, ac-
cording
with,, 'water)
to the followidgjeaction:
CH-10/-10-Tge 37
4ditty ti
4
f
Ain
SI(1-13)2SiC12 hH20
Dime.thyldichlorosilane
[(CH3.)2SiO]n + 2n HC1.
Silicone Polymer
The polymerliation occurs at elevated temperature in the
..prdsence of borit acid as a catalyst.
CAUTION:' THIS EXPERIMENT MUST BE CONDUCTED IN THE
HOOD. THVE MA' BE NO FLAMES IN TBELABORATORY. ETHER
IS FLAMMABLE, AND ITS VAPORS CAN'BE EXPLOSIVE.
1. Add 40 mrof ether to a 250, ml Erlenmeyer flask.
2. Add 20 ml of diknethyldiChleroilane to the ether, acid
mix by swirling.
3. Dropwise, slowly add 40 ml of water. (If the water is
added too rapidly; the reaction will get hot, and the
reaction mixture will bubble out of the flask.)
Transfer the, mixture to a 125 ml sepratory funnel and
separate the ether layer from the'water layer, keeping
the ether layer in thefunnel.
5. .Cautiottsly wash theether layer with'a saturated sodi-
um bicarbonate solution, being careful to allow the
carbon,dioxide that is generated to escape without
allowing the solution'to bubble out cif, he ,separatory,
funnel. Add' 10ml of the bicarbonate s iution at a
time, swirling the funnel until the carbon dioxide is
no longer formed.
6. The purpose :of'the'sodium bicarbonate solutionis to
neutralize,-the hydrathloric acid formed in the poly-.
e-meriAation. Test one drOp.of-tfle soliition with litmus
paper. Continue washing with'sodium bicarbonate until
the acfueous phase is no longer acidic.
Page 38/CH-10
00.
'V
V
7. Remove the ether layer And transfer it to a dry 125 ml.
-*Erlenmeyer' flask which contains
0l'' fib of anhydrous Na2S3),..
,
8. Allow the ether layer to dry for about:15'minates .(by45
.being in contact with the'anhydrous Na2SO4).
9. .Put 'the ethers into a 150 ml beaker%and evaporate tkii:,
ether by placing the 150 ml beaker in a 400 ml beakers
'of-hot water. CATUION: DO NOT USE `A FLAME TO HEM'
THE WATER.-c
10. When all of the ether has "evaporated, obtain the weight
of the silicone oil.
11.' Calcullate the weight of 5% of the silicone oil and add
this amount of boric oxide to the silicone oil while
stirring continuously. Continue to stir for several
minutes after the addition of the boric oxide.
12. Transfer the mixture to a test tube and heat- in an. oil
bath at 200% fox three to four hours.
13. Remove the test tube and cool it; then examinecthe on-
tents.. This putty differs from the commercial product
since it lacks additives that enhance the mechanicalI strength.
REFERENCES '
Arnol,d, Lionel K. Introduction to Plastics. -Ames, IA: Iowao
State University Press, 1968.
Bikales, Norbert.M., ed. Adhesion And Bonding. New York:
John Wiley & Sons,,Inc.01-1971. #
Brewer, Allen F. -Effective Lubrication. Huntington, NY:
Robert Krieger Publishing,Co., 1972.
Cagle Charles V. Adhesive Bonding Techniques and Applica-
tions . New-York: Mc,Graw-Hill Bdok CO.,' 1968.,
"0
216CH-10/Page 39.
f
Crosby, Edward G._and Kochis, Stephen N. Practical Guide to
Plastics Applications. _Boston:. Cahners Books, 1972.
unther, .Raymond C. Lubrication. Philadelphia: Chilton
.Book Co., 1971.
':.Katz, Irving. Adhesive.Materials; Their Properties and
Usage. Long Beach, CA: Foster Publishing to., 1971.-
0
Page 40/CH-10
^ C
I
217
4.
GLOSSARY
Adhesive:, A material used to join components.
Copolymer: CombinAion of two or mere polymers.
Engineer.ingylastics: Pilastics that have outstanding mechan-ical, electrical, and chemical characteristics.
Friction; A *force that tends to interfere with the motion of.two objects that are in contact with each other.
Glass transition temperature: The temperature at which a- plastic softens Dr melts.
Lubricants: A substance used to reduce friction.
Monomer: Starting material for making plastics:
Plasticizer:. A chemical added to plastics to help keep themfrom getting hard and brittle.
Polymer: A long-chain organic chemical plastic.,.
Stabilizer: A chemical added to plastics to retard deterio-ration'due to sunlight.
'Thermoplastic: Plastic that will'often when heated.
h.
Thermosetting plastic: A plastic that hardens through chem-ical reaction and will not soften under heat.
.
4
e
1.
A
iP
4
CH-10/Page 41
4N1.
INTRODUCTION
1,
I As was learned from earli, 'module, chemical reac-
tions involve the interaction o elections in atoms. These
11.
electrons are found in ene shells rrounding a nucleucS.
In general, chemical reactions involve the gain, loss; or
1
sharing of orbital electrons by atoms. Nuclear chemistry
(or nuclear physics), however., deals with what happens to
1
the nucleus of atoms. In ordinary chemical reactions, the
atoms taking part retain their identity; in nuc ear reactions,. new elements are often formed.
Nuclear reactions are accompanied -by energy changes
that are several orders of magnitude greater than those as-so-
!ciated with ordinary chemical reactions. For example, the
energy evolved when one gram (g) of radium undergoes radio-
active decay is about 5001e00 times as great as that given- -
off when an equal amount of radium reacts with chlorine to
form radium chloride. Still larger amounts of energy are
given off in nuclear fission and-nuclear fusion reactions
a fact that insures their importance today. In fact, nuclear
energy has"the potential of supplying much of the woYld's
energy needs, providing that associated problems can be solved.,
This module is a study of radioactive igotopes (which are
widely ed in medicine, industry, and chemistry), as well
as fission and fusion processes,
PREREQUISITES
The student should have completed Modules CH-01 through
CH-05 of Chemistry for Energy Teanology I and Modules CH-'06
through CH-10 of Chemistry for Energy Technology ff.4
0
220'CH-11/Page 1
OBJECTIVES
'Upon completion of this module, the student should beable to:
1. Define the following terms:
a. Critical mass.
b. Chain reaction.
c. Breeder reactor.
d. Alpha particles.
e. Bdta particles.
f. Electron capture.
g. Positrbn,
h. Half-life.
i. Fission.
'j. Fusion.
k. Gamma rays.
2. Complete and balance nuclear reactions.
3. Use-the half7lie of a substance to predict the amount
of radioisotop ent after a period of time.4. Use Einstein's mass ergy relationship to calculate
the energy change, or mass change, of a nuclear reac-tion.
5. Describe the design of a nuclear power plant and explain
the role of control rods, cooling fluid, and fuel ele-
ments.
6. Describe fusion and fission nuclear proNsses.
400
Page 2/CH-11
.22j
= \ ,
SUBJECT MATTP
NUCLEAR CHEMISTRY
iOrdinary chemical reactions involve only the electrons
in the outer shell of atoms. N clear chemistry deals with
certain unstable atoms that can emit various particles and
rays and, in the process, be transformed, from one element
into a different()
element. The property of emitting particles
and rays from the nucleus of an atom is called radioactivity.
Nuclear xeactions in which the action is spontaneous, known
as "natural radioactivity, cannot be speeded up or slowed
down by any physical or chemical means. Artificial radio-
activity:, produced when substances are made radioactive by
bombardment with particles Such as alpha particles, protons,
electron's, and neutrons, is of extreme importance.
Nuclearereactions differ in another important way from
ordinary:chenfical reactions that'is in the amount of
energy released. In nuclear reactions, matter is converted
into energy, thereby 'releasing tremendous amounts of energy.
The energy relesed by nuclear reactions dwarfs th'e energy
produce& by.chemical reactions.
The nuleus is composed of two types of large particles,
protons -and neutrons, as well as many smaller particles.
The proton is poF:itiIely charged and has a relative weight
of appr6ximately one atomic mass unit (amu). The neutron
also has; .a relative weight of approxim4tely one amu but it
neutral. The mass number of the atomic nucleus is the
number af,rarticles, or nucleons. The-refore, the mass number
is equal to the number of protons plus the number of neutrons.
Furthermore, the number of protons is equal to the atdMic
number of the element. From earlier experimentation with
the scattering of alpha particles, it was concluded that
222CH-11/Page 3
the nucleus occupies only a very small fraction of the volume
of an 'atom and'that its very compact. Nuclear radii do not
exceed 10-12 cm, whereas atomicinveslarger.
NUCLEAR RADIATION
Some nucleii are unstable and spontaneously' emit particles
and radiation. The discovery of this natural radioactivity
is credited to the French scientist, Henri Becquerel, in
1896. Becquerel's research was spurred by the discovery
of X rays by W. C. Roentgen earlier that same yeat. Becquerel
discdvered that uranium produces a spontaneous radiation
that can develop an image on a photographic plate.
An unstable nucleus can be transforMed into a stable,
one by:the emission of particles or radiation. The three
most common types of radiation emitted by radibactive sub-
stances are alpha particles (a), beta particles (a), and
gamma rays (y),.
Alpha rays are particles consisting of two protons and
two neutrons, having a weight of four amu and a double posi-
tive 'charge. Alpha particles are identical with the helium.,
nucleus; that is, they are helium atoms_that have lost.their
two orbital electrons to form the doubly charged ion, He++
.
These particles are traveling at a speed of up to 20,000
miles per second as they leave the nucleus. 'However in wl
spite of this speed and their mass, they are not especially'
penetrating. Alpha particles will travel only a few centi-
meters in air before they are stopped. Items such as paper,
aluminmi'foil.,-or rubber gloVes will stop them: Radioactive
decay, through the emission of alpha rays, is shown by the
Page 4/CH-11
2 03
p.
,
'-
following reaction:N
Alph-aemisslanzz----2ii-Rn---oo---e-ttro A- '1-He
1
'
This reaction illustrates the type of equation used to de- ,
note nuclear reactions. The symbol 2i6Rn denotes the isotope'
1
,
of radon (Rn), which weighs 222. The 86 is the atomic num-
bdr of.radon. Radon disintegrates to form plutonium (with..,
Ia mass number of 218 ad anatomic numb sr of 84) and the
alpha plIrticle He (with a mass number of 4 and an atomic
I
,Lnumber of 2). Note that the subscript and superscript nu*.
bers on each side of the equation must balance. For example,4.
the masses of Po and He e al the mass of Rn, as follows:
I .
,.- 222 = 218 + 4
In addition, the atomic number must balance, as follows:
86 = 84 + 2
Nuclear equations can often be completed through such a
balancing process.
Beta rays are streams of electrons traveling at enormous
speedS (approaching the speed of light). These electrons
coming from the nucleus are'not the orbital _electrons. How
can .electrons come from the nucleus, which supposedly is
composed only of neutrons and proton's? Emission of beta
particles can be considered to be the result of the conver-
sion of a neutron into a proton and an electron, as Shown
below:
111*
P0+ _le
CH-11/Page 5
224
CA
In this process,"the neutral neutron (weighing one amu)
is converted into the positive proton (weighing one amu)
---a2..r14thenegativc clectrono1.betaparticle (weighing lessthan one amu). The weight of the electron is 1/1846 that
of the proton; therefore its weight is negligible, compared
to the weight of the /5roton or the neutron. This nuclear
equation is balanced since the masses on either side of the
equation are equal:
1 = 1 + 0
The charges are also balanced as shoWn below:
0 = 1 + ( 1)
The protonswain in the nucleus, whereas the beta rays
are shot out 00 the nucleus at high speed. Beta rap are
many times more penetrating than alpha rays because the beta
rays travel at-much faster speeds. An' example of beta emis- c
sion is the sponaneous radioactive decay of thorium 234 to
protactinium 234:.
2nTh 29iPa + -1e Beta emission
Note hat,in beta emission, the negative electron leaves
the nucleus and that the positive proton formed inthe pro-
cess increases-the atomic number byitne unit (in this example
from 90 to 91Y. Therefore, a new element is formed through
beta emission.
Gamma' rays consist of electromagnetic radiation of very
shor,t wavelength. Gamma rays have no>charge or particle
behavior; they act as true waves. Gamma rays can be compared
Page 6 /CH -11225
0 .
to X rays, except that they have even shorter wavelengths
and, therefore, are much more penetrating. These rays pre-
sent the main danger in working with radioactive materials
since they can easily penetrate the body and can,cause serious
physiological damage. It requires alinCist a foot,of lead
or several feet of concrete to shield against gaTma rays..
Gammaradiation is not generally shown when writing nuclear
equatio since charge and weight do not eligiZtn,gamma.
emissioi However gamma emission is usually accompanied,
by other radfoactive emissions.
The effect of an electrical'
field upon alpha, beta, and gamma
emissions is illustrated in Fig-
dre 1.
In addition to 'alpha, beta,
and gamma radioactivity,,,there
are two other decay'processes:
positron emission and electron
capture. A I5ositron is a par:
ticle that has the same mass as
an electron but an opposite4
(positive) charge. The symbol Figure 1. Alpha,'Beta
for the pogitron is .1.g.e. Carbon-and Gamma Rays in anElectrical Field.
11 is an example of an isotope
that decays by positron emission:
Positron emission
Positron emission can'be considered'to be the conversion of
a proton into a neutron and a positron:
p Positron formation
Proton Neutron Positron$
Ch-11/Page 7
4_
oiMMMOTSIII1
I
The energy level, or shell, nearest the nucleus is known
ds the K-shell. It is potsible for the nucleus to "capture.____
. Ione of these K-electrons in a process called electron capture.
For example, vanadium-49 can capture:a K-electron to become.
_ .titanium-49:
..A ,
ea, NV -P ...2e,-----31-nTi Electron k- captureI
0 K-electron
Electron capture may be thought of as converting a proton
to a neutron as follow's:6 I
ip _?e in
RADIOACTIVE DECAY SERI-ES1
. As indicated earlier, unstable nuclei,. can lose particles
or radiation and bedome stable. Often, this may involve
more than one step. For example, Figure 2 shows uranium
c.an'decay in a series of Steps until, finally, lead-82 is
formed. In the first step, uranium-238 decays through alpha
emission to form thorium as -follows:
23!6 234mt.90111 211e
Then,,the thorium-234 decays by bibta emission:
f 2 o Th 2 3 i Pa _le,
The'decay continues thrOugh 13 or - 14 steps, depending upon
the .specific route taken (Figure 2),.until 1N-206 is formed.
Page 8/CH-11
41
2271
238
. 234
2:10
.228co
w .
mi 2222
z -s, 208
co
2 '214
210
2.0880HG 1.1
A
/77
82 84 88 '88 9081 AT FR ACPS PO RN RA THATOMIC NUMBER
92PA li
z
Figure 2. Radioactive DecaySeries for Uranium-238.
.
(In Figure 2, the ort, horizontal arrows pointing to the
right indicate beta emission, and the long arrows pointing
down and to the left correspond to alpha emission.)
HALF-LIFE
Each nuclear decay. reaction has.,a characteristic decay
time. This reaction rate is usually expressed as the "half-.
life." The half-life .is the time required for half of a
given quantitot a radioactive substance to react. Each
228
CH-11/Page r9
4..,
"sisotope has its own .characteristics half-life. For example,
the half -life of strontium-90 is28 yeais. if one started ,
. with 100 g of strontium, after 28 years, only 50 g of stron\
tium would remain. Xhe'other 50 g of strontium, would have
been converted to yttrium-90 through'betadecay, as shoWnAby the following redttion:
,.,)
% \, \
After anotherhalf-life period (28 years), only 25 g of the
strontium-90 would 'remain. Half-lives of the radioactive
.element.Vary wide-y 7 from as short as millionths of a sec-
ond to as long as illions'of years. The rate of disintegra-
tion of a radioactive material cannot be increased;. there-.
fore, the material must be stored prOperly to allow .it to..
become non-radioactive. , Unfortunately, it may.take millions- -; .
of years for some%radioaatfive.wg.stes to decay. to safe `levels.,,
In-the meantime, they must be contained go they are not pe-.
leased into the environment .
Ah interesting application of natural radioactivity.D .
has been in its use to determine the age of the earth. Ii
this procedure, the radioactivity of a given isotope is mea-
-tured and its half -life is used to calculate the time the
isotope has been in existence. For example, one g of uranium-
238 would produce 0.43 g of lead-206 and 0.067 g of helium,
leaving 0.0.0 g of uranium-238 after one half-life - or 4.5
billion years. By comparing the amount of lead -206 to the
amount of uranium-238 in-a minetal,°tge age of the rock can_
be established. This analysis indicates that-the age of the
earth's crust is approximately 2:6 billion years,0
The half-lives and types of decay processes are givenrfor some artifical and natural radioisotopes in Table 14'
Page )0/CH-11 2294
03
TABLE 1. HALF-LIVES AND DECAY PROCESSES OFSOME RADIOACTIVE ISO'T'OPES.
_Isotope Half-life Decay Process
Artificial
R4dioisotopes
1.
,
Plutonium-239
Cesium -13?
Strontium-90
iodine-131
24,000 yr ,
30 yr
28 yr-,.
8 days
i.
''Alpha
Beta
Beta
Beta\Natural \
Radioisotope
\
Thorium-232
'Uranium-238
Potassium-40
\Carlitn-14
1.4 x101° yr
4.5 x 109 yr_
1.3 x 1g9 yr
5,700 yr
*Alpha
Alpha
Alpha
Beta
,' .
DETECTION OF RADIOACTIVITY
Alpha, beta, and gamma .rays ill interact with the atoms
of matter by dislodging orbital electrons, thus forming ions.
The,aMonnt of pdiation, therefore, can be deterMined by\
the amount Of ionization produced by the radiation. Not0
all interactions between radiation and matter cause ion forma-
,tio. In'4.cme:cases, electrons can be raiSed to higher energy
Levels (shells) , When these electrons return to. their normal- ,
Nenergy .leve , trays, ultraviolet, or' visible light may be
emitted, dep on the energY'levelA In addition, some
of the energy of the partiEleTof radiation may appear. as
. heat.
Although one cannot see, hear, feel, taste, or smell'
radietioh,there are a number .of methods used to \det'ect it.
No.
C1-011/Page-11
230
AP
/-
1.' Photographic plate's and film have been used to detect
radiation for many years. The radiation affects,
photographic film in much_the same way as ordinary
light. the darkening of film cangive a qUantitative
measure of the amount of radiation to-Which the film.
has been exposed. it is common practice for people
who work with radioactive substances to wear film badges
to record the amount of,radiation to which they have f,
been'txposed. r
2. Historically, cloud chambers have been used to detect
radiation.- In the cloud. chamber, the ions prociuced.
by ionizing radiation pass through a sUgeTsaturated) to
vapor. -The.ions from the radiation become nuclei for
the production of. liquid droplets, which form a cloud-
like track. The cloud chambger can be placed in a mag=
netic or-electrical field to assist in determining the
type of'_rad.iatiOns present .
,3. The Geiger - Mueller counter (or, simply, .the Geiger ,
counter) is themost common device for detecting and
Measuring radiation. The, Geiger counter consists of
,a cylindrical Cathode with a wire anode running along
its'ax,is. The anode and cathode are sealed in a gas7
filled glass tube. An electrital potential difference
is maintained between the anode and the cathode. This
potentiil is-just slightly below that required to pro-
_ ',duce an electric discharge in the gas. When ionizing \
radiation enters the tube, it causes the formation of
ions which, in turn, causes an elettrical breakdown
of the gait tending e pulse:of electrical current to
,a counter. A schematic representation of a Geiger counter'
.-- is shown in Figure 3.
Page 12/CH-11_
.'r 231
'Figure 3. Geiger Count
4, . In the scintillation counter method of radiation de,-
tection, dials of luminous watches are painted with
a mixture Of zinc Sulfide (ZnS) and radium sulfate
(RaSO4). The zinc sulfide fluoresces, forming visible
light when struck by' the radioactive missions from
the radium. The visible light may be focused upon
photomultiplier, enabling the radiation to be Measured.
People are constantly exposed to natural radioactivity.
This "background" radiation comes from cosmic rays, ultra-.
violet light, and radioactive elements such as uranium in I:
minerals. The level Of this radiation varies with the amount
of exposure to the isunjand other light sources and with the
elevation above seal level. Concern has been expressed because
of the increased' exposure to radiation from artificial radio-'.
activity. Tho/interactions of radiation with living matter.
are the same as wit Other molecules: ionization, molecule
ekcitation, and heat generation. It is known that large
amounts of radiatiori kill organisms, but the safe level of
radiation above background' level is note well' established.
Even_slightxposures (including background radiation) can
cause changes in cell chromosomes and, thut, cause birth
CHIll/Page4.3
232
rt
defects, leukemia, bone, cancer, and other forms of cancer.
The benefits to be derived from certain radiation exposures,
such as dental and other medical X rays, must be weighed
against possible risks of such exposure. Because of the
uncertain effect of prolonged radiation, it-seems prudent
that extreme care be exercised in the use of-radioactive
materials.
NUCLEAR REACTIONS
In nuclear reactions, mass is converted to energy.
Einstein, in his theory of relativity, related energy and
mass by means of the following equation:
E = mc2 Equation 1
where:
E = Energy, a unit called ergg'.
m = Mass, in grams.
c = Velocity of light, in cm per second.
The fact that the velocity of light'is high (3 x 101° cm/sec)
and term s squared in Einstein's equation makes it evi-
dent that a tremendous quantity of energy results from the
destruction of a small quantity of matter. Consider the
amount of energy associated with the alpha decay of uranium-.,
238. The nuclear reaction for the decay may be shown as
follows:
2381192u
'Page 14/CH-1,1
290ThI+rt-n +9 0 1.
-2he
233
+ Energy
1 .
OP
The masses of the atoms are as follows:
,291U =4238.0508 29oTh = 234.0437 nie = 4\,0026
Now, 234.0437 + 4.0026 = 238.0463. The 238.0463 is 0.0045
amu.l.ess than,238.0508. Theref6r 0.0045 amu was lost
during .the decay process and conver ed to energy. This
kinetic energy is Carried away byt the alpha particle. Using
Einstein's equation and using the conversion of amu to grams,
one obtains the following:
E = 0.0045 amu x 1.661 x 10-2' g/amu
x (3 x 1010)2 cm2/sec2
= 6.7 )e, 10-6 erg.
4
Converting the erg value tomillion electron volti (MeV)
gives the following:
= 6.7 x 10-6 erg x 1 MeV/1.6,02 x 10-6 erg
= 4.2 MeV.
r.
This calculation and similar calculations indicate the tre-
mendous,energy involved in nuclear reactions. For example,
the energy released though the nuclear reaction of one pound
of uranium is equivalent to that released by combustion of
1500 tons of coal.
NUCLEAR FISSION
wheh certain heavy elements, such.as uranium-235, ura-
nium-233, or plutonium-239, are struck by slow-moving neutron's,
CH-11/f3age 15
the nucleus is split into two large particles a1;\, 1 the
average, 2.4 neutrons. Three possible reactions arei0i-.
cated as follows:
in + "231U
1492D2na nicr 3 in
302n 16620m0c,4 in
In Cs + . 2 in
.Figu're 4 illustrates the first reaction above in which.
a thermal or slow-moving neutron strikes a uranium -235 atom,
causing it to split into barium-142, krypton-91, and three
more neutrons. .This process in which a large atom is split
into smaller fragments is known as nuclear fission. It
is the basic reaction that occurs in the atomic bomb and
nuclear reactors for generating .electricity.
More than 200
different isotopes
of 35 differerit ele-
ments have been
found among the fis-
-sion products of
uranium -235.
On the average,
Figure 4., Fission of Uranium -235. ,2.4 neutrons are pro-
.
duced by every fis-
sion of uranium-235. If one fistin producet two neutrons,
these two neutrons can cause two additional fissions, releas-
ing four neturons. The four neutrons can then produce four
more fissions and so ,forth, as illustrated in Figure 5.
The number of fissions and their associated energies
quickly escalate and, if left unchecked,, can result i4,an
explosion. This process is called a chain -reaction. A
Page 16/CH-11
a
a
certain mass of fissionable
material must be available
for the reaction to be self-
sustaining. Thii mass;
called the critical mass, is
required id that the emitted
neutrons have the opportunity .
. ,
to strike other atoms before
they escape from the sample-.
In the atomic bomb, two sub
.critical masses are bought
together by a chemical ex-
plosive to form a critical
Ql.e.eniYiele
IUIF itit/eNUCLEUS / . 0 .NEUTRON \--4.-----40
IN 0 ) 2 NEUTRONSFROM FI4SION
1
mass. Only 6000 g of
plutonium-23 are required
to form a'critical mass. The
small size of this critical mass needed to form an atomic,
bomb has caused fear that enough material to build a bomb
could easily be stolen'
Figure 5.Chain Reaction.
NUCLEAR FUSION
Light atoms can combine under certain conditions to
form heavier atoms, with a release of tremendous amounts
of energy; This process is called nuclear fusion. Nuclear
fusion occurs in the sun and in the hydrogen bomb. If the
fusion reaction can be controlled, it can produce an almost
Unlimitedqamount of energy. One of the most important fusion
reactions is the following:
H- + IH in + Energy
236
CH-11/Page 17
The iH atom is called heavy hydrogen, or deuterium. About
0one atom, out of every 7000 natural hydrogen atoms is deuterium.
Deuterium has one proton and one neutron, whereas normal
hydrogen has only a protOn and no neutrons. Deuter-ium is
obtained by the electrolysis of water. Water molecules,
which contain deuterium rather than normal hydrogen, are,
slightly more difficult'to decompose with a Current than
regular water. Therefore, when water is broken down into
oxygen and hydrogen by electrolysis, the last small fraction
of water that remains undecomposed will be rich in water
containing deuterium. Then, by electrolyzinethis remain-
ing water, nearlNoure heavy hydrogen can be obtained.' The
second atom in the preceding reaction, iH, is called tritium.
IL i ium anextremelyrareis otop ee f hy
tains one proton, and two neutrons in the nucleus'. The com-,
bination of deuterium acid tritium forms 11.61ium,a neutron,
and tremendous quantities of energy.
The fusion reaction-is an appealing source,of energy
&ince the light isotopes are readily available and the fusion'
products are generall not radioactive. . Since deuterium
comprises about one in every 7000 ,hydrogen atoms, the oceans
can supply an almost limitless amount of nuclear fuel. The '
tritium for the hydrogen fusion reaction Canbe obtained
from liquid lithium, which can serve for both'a heat trans- .
fer.medium and a tritium source. The tritium can be obtained
through the following reaction:
3:Li on 0- He on
It is estimated that there is sufficient lithium on the earth
to provide a source of tritium for energy production for
about one million years.
Page 1.8 /CH-11
237d.
Although the fusion reaction holds much promise for
providing unlimited quantities of energy,there are many
technological problems that must be overcome before the po-
tential of fu 'on'reaction's is realized. Extremely high
temperures a e required to trigger the fusion reaction.
Temperatures in ,excess of 40,000,,G00°C must be reached to
permit th fusiori reaction to occur. Currently, the.only
known means to achieve these temperatures is th-iough a fis-
sion bomb. In the hydrogen bomb, these'high temperatures
are attained by exploding an atomic bomb, which then triggers
the fusion reaction. There is no known, container material. that can be used to contain a substance at these fantasti-
cally high tempeiratures. Therefore, a method must, be devised
to confine thmaterials out of contact with other materials
and still maintain a high enough densitY to permit the fusion
reaction to occur. Two methods are under investigation:
confinement in a magnetic field and heating a frozen deuterium-
tritium pellet with a laser beam. Although there is reason
for.a limited amount of optimisle, it is impossibleto know
at'this time if fusion'reaction will ever become'a,practical
source of'energy.
NUCLEAR REACTORS
Nuclear reactors convert the heat that is produced by
the fision of urani m-235 into steam which can then be used
to generate. electricity. Figure 6 is a schematic of a milear
reactor ,of the pressurized water type.
CH-11/Page 19
(CONTROL RODS
WATER AT 300C
REACTOR
FUEL ELEMENTS
PUMP
RECIRCULATED WATER
STEAM TO--...\ GENERATING SYSTEM
HEAT EXCHANGER
Figure 6. Nuclear Reactor.
WATER
This type of reactor is the most common type used in the
United States. At a pressure of 2000 psi, water is passed
through the reactor to absorb the heat given off by the fis-
,sion process. The water, coshing out of the reactor core
at a temperature of 300°C, is circulated through a closed,
lobp that contains a heat exchangei. A 'second stream of
water .at a lower pressure passes through the heat ex-,
changer and is converted to steam at 270°C. This steam is
then used to drive a turbine to produce electrical energy.
Nuclear power plants have several advantages over conventional
coal- or oil-fired power plants. Onp major advantage is
the relatively low fuel co-st compared to conventional fuels.
,Page 20/CH-11
230.t4
O
tr.
The uranium used in a nuclear power plant accounts for only
about 20% of the cost of eictricity produced, whereas fuel
costs in other types of power plants account for about 40%
of the cost.of electricity produced. Another advantage
attributed to a nuclear power plant is the low amount of
emissions it discharges into the atmosphere, as compared to a
fossil fuel plant, which can discharge several hundred thou-
sand tons of sulfur dioxide; nitrogen oxides, and ash particles
into t atmosphere each year. The most serious problem
associdted with nuclear reactors is the hazard from the
radioactive products of the fission process. Large amounts
of these products are obtained, and safe, long-terRAstorage
of these wastes is a serious problem. In addition, there
is always the possibility that an accident at a nuclear power
plant -could occur, releasing dangerous amountsof radioactive
materials.
As indicated in, Figure 6, the nuclear reaction is con-
trolled by rods that can be lowered into the fuel elements.
A These control rods are made of cadmillm, which absorbs neu-k
trons very effectively. During start-up of the pdwer plant,:
the control rods are gradually raised, allowing the fissfon
reaction to start. By careful manipulation of the rods,
a steady state is reached whereby, the heat that is generated
is balaarea by the heat that is carried off' to the heat ex-.
changer. Thus, the reaction proceeds safely with no danger
that the reactor will explode.
BREEDER REACW/Ra..
It has been estimated that in less than SO )(ears all
of the uranium-235 in the United States will be.depleted.
240
C--
CH-11/Page 21
Only 0.7% of all uranium is uranium=235; the remaining 99.3%
is uranium-238. In .conventional nuclear reactors, uranium-
235 can be split rather easily with slow-moving neutrons; lilyk
but uranium-238 will not undergo splitting with slow neutrons.
However, it may be possible for the neutrons given off by
the 235 isotope to cause fission of the 238 isotope, accord-,ing to the following reaction:
238u .+9 2 On --0-2 Pu + 2 e
The plutonium-239 that is formed can readily undergo fission,
according to the following reaction:
2319+PU1" 9 00,1 38ar l'aBa +' 3 111
Theoretically, it is possible-that a reactdrutilizin these
reactions could prod' 'e more fuel, than it consumes. Thus,
these .qctors are calle reeder reactors. Breeder reactors
are currently under development, but they pose many technical
problems. For instance, these reactors use liquid sodium
as the cooling medium. Sodium is extremely reactive and
causes severe corrosion problems. In addition, the plutonium
is an extremely dangerdus radioactive material.._.._ Because
of its long half-life (24,000 years), any accident involving
plutonium could eave an_affected area almost permanently
contaminated.
Page 22 /CH-1T 241
ti
4k
RADIOISOTOPES
a
Radioisotopes-are widely used in medicine and industry.
Cobalt-60 is used in the treatmenVof cancer to destroy or
slow the growth oftmalignant tissue. The basis foT such,
treatment is the fact that, although gamma radiation tends,.
to destxoy.all cells, cancerous cells are more easily dw
stroyed than normal ones. Trace amount f, radioactive
materials can be injected into the blood stream, and any
build-up of Yadiation can pinpOint problets such as circula-
tory disorders. Industrially, radioactive isotopes are used
to measure frictional weir and corrosion rates. -The thick-
ness of very thin ,sheets of metal, paper, oitplastic cam.
be,&asured by plating them between a radioAtive source
)
and a deteCtorosuch.as'the 'Geiger counter. The amount of
radiation passing - through' the material is a measure of its
thickness. This metho4 can be used to nondestructively test
fot,fliw.i in many materials. Neutron activation analysis
is an important analytical technique. In this procedure,e:
the sample is bombarded with neuzzons, and the element of :Y
An-ter-estis converted into a radioi'sotoPe. A measurement
.of the radioactiyfty5f the isotope can then be used to-cal-
culate the amount'of tip-element in the sample. This method
of afalysis'is especi,lly attractive for twc reasons: it
can be used to determ ne trace amounts of an, element and
it is nondestrugive.
a e
CH-11/Page'23
(
. EXERCISES
1. Complete. the following nuclear reactions:
a. 23Co ? 'iHe
b. 2351192u 2me
c. iNg + + ?
. 2. % The half-life of hydrogen-3 is 12.3 years. How much
of a 50 mg sample will remain after 24.6 years?
3.04eGiven the following atomic masses
I .
iL
1Li = 6.01513
1He = 4.00269
iH .5.3.01604
an = 1..008665
. calculate the amount of energy in million electron
volts (MeV) *given off in-the folloWing nuclear re-
action:
..,
'O. Write an equation for each of the following radioactive
I
...
decay processes:
.
-a. K-capture of 24Cr .
ID. Beta-decay of Ilic
c. Alpha emission of 99Ac
S. Radium has a half-life o 690 years. Starting with
20 g of radium, how. mucti.rad'um would be left after...--r-L.
-a. 845 years?.
b. 1690 year's?
- c. 3380 years?
243CH-11/Page 25
Q
LAIDRATORY MATERIALS
Laboratory 1 Laboratory 2
Geiger counter Geiger counter
Radium dial watch Watch gl3s
Meter stick Separatory fu
, Cardboard Pipette
Radiavtive ores P ette bulb
Aluminum foil
Lead foil
Gamma source
Potassium iodide
Radioactive potassium iodide
Carbon tetrachloride
Bromine water
SZN4hydroxide, 0.2 M
LABORATORY PROCEDURES
LABORATORY 1. RADIOACTIVITY.
The radioactive samples of ore used in this experiment
are available from chemical supply houses. They present
np particular hazard; however, it is good,to develop and
use the sametechniques and precautions that must be used
with other, more dangerous radioactive materials. Precautions
and disposal sugges0.ons shOuldbe found in,the literature
available with t samples. The radioactive samples will
give off bet nd gamma rays. In this experiment, ,the shield-
ing effects of cardboard,, aluminum, and lead will be examined,
using:a Geiger counters A graph of radioaftivity versus
distance from source will then be constructed.
'Page 26 /CH -ii 244
PROCEDURE
1 If the Geiger countr is of the 11 -volt type, plug
it into the power source.,
2. When the counter has warmed up (immediately, if it is
battery powered), hold the probe toward the ceiling.
The clicks that will be heard are from natural back-
ground radioactivity.
3. Place one of the radioactive samples on e laboratory
bench and position the probe th ee feet (ft) from the
sample.
4 Count the clicks (or flashes) heard for one minute
(min). Record the number Of clicks.
(1 min at,3 ft)
5.. Positibn the probe one foot from the source and count .
the clicks for one minute.
(1 min at 1 ft)
6. How does distance relate to the number of 'clicks?
'
7. Place a radium-Adial watch one foot from the4probe and
observe the /4d4vactivity, as indicated by the counter.
Compaie the intensity of radiation of the ore sample,
with the intensity of the radiation from the watch.
8. 'Place a piece of cardboard between the probe-and the
ore sample. Count the number of clicks for one Minute,
at c1 "e foot and three feet.
(1 min at 3 ft, with cardboard)
(1 min at 1 ft, with cardboard)
245A
CH -11 /Page 27.
0'.
O
Jib
49. Placela piece of aluminUm foil between the probe and
the pre sample. Count the number of clicks for on
minute at one foot and three feet. .
(1 min at 3 ft, with aluminum foi14
(1 min at 1 ft,, with aluminum -foil)
10: Place a piece of lead sheet between the probe and the
ore sample. Count the number of clicks for one.minut.e
4 at one foot and three feet.
(1 min at 3 ft, wj.th lead shdet)
(1 min at 1 ff, with lead sheet)
11. Compare the.intems.ityof radiation striking the un-
shielded probe to that striking the probe when shielded
by the materials'in Steps 8, 9,-and 10.
12. Close the.shield covering the probe-to prepare the://1
counter for us& with the,gamma source.
13. Place the gamtha source 5 tm from the probes and remove
for a second minute, and for a,third minute, recording 1the shield. _Count the number of clicks for one miriute,,s
the data below. . Average the three values and record
the ayerage. Repeat these m drements after moving
the gamma source, further awa
ea
1 cm at a time until
the source is 20 cm from the probe..
Page 28 /CH-11
0
2I6
v.
?"'
bistance from Clicks/ -Clicks/ Clicks/
Probe (cm) Minute Minute Minute Average
Sry
6
7
8
9
10
11
12'
13
14'
.15
16
..17
18
19
20
14. On a sheet of raphpaperplot a curve of tivity
versus distanceof source to the probe -, Plot'the num-
ber of clucks (activity) on the y-axis, hnd the dis-,
,.tance' (in cul) on the x-axis. Note that the curve is
not a ,simple inverse proportion. TMcurie illustrates
the law of inverse squares for radioactivity.
k
.LABORATORY -ISOTOPIC,PROPERTIES (Demonstration).
ThiS experiment illustrates that the chemical.properties
of.radioactive isotopes, are identical to the chemical prop-.
I erties of non/radioactive isotopes.
247 CH-11/Page 29
PROCEDURE
1. Dilute a small amount ofathe radioactive potassium
iodide solution,(less.than one microcurie) with five
drops_of thre sodium hydroxide solution.
Z. AUd'a small crystal of non-radioactiVe.pdtassiuM iodide
and stir until it dissolves.
3. Position the Geiger counter probe 5 cm from the radio-
active mixture and note the activity.
4. Pour 10 ml of the'solution into the separtory funnel
and add a few diops of bromine'water. (The bromine
should react with the iodide ion, converting it into
free iodine.)
5. Add 10 ml of carbon tetrachloride. Shake the mixture
and let it stand. (The lower" layer of'liquld in the
funnel s'hould indicate the chirateristic iodine color.)
6 Draw off the bottom liquid into a small beaker and test
its activity with the_Counte.
7. Answer the follOwing queitiods:
a. -Toes thebottom colored , layer contain-radio-
activity?
b. r.Do radioactive and non-radioactive compounds mix
in solutdonl
Did the iso pic 'forms of iodine accompany each
other through' he extraction?
Do radioactive and non-radioactive isotopes have
the-same chemical properties? Do they have the
'sate physical properties?
e. Describe the difference betweeen radioactive and
non-radioactive isotopes.
a
Page 30/CH-11
14
%.
248
4
REFERENCES
Aryei, E. and Scarlett, C.A. Energy Sources' The Wealth
of thd World. New York: McGraw-Hill Book Co., Inc.,
195k2.
"Breeder Reactot s Hold_Key_to_Energy_Needs:"__Chemical
Engineering News (December 1962) p. 21.
"Energy." A special issue of Science 180, 4134 (1974).
Gregory, Dereck P. "The HydrogenEconoty." 'Scientific
'American 228, 1 (1973) p. 13.
Leachman, R.B. "Nuclear Fission." Scientific American
(August 1965) .
Linnenbom, V.J: "Radioactivity and the Age. of the Earth."
Journal Chemical Education 32, 58 (1955).
fo,
70,
1
CH-11/Page 31
<
16.
GLOSSARY
Alpha rays: Particles consisting of two protons and twoneutrons,.
Beta rays: Streams of electrons traveling at enormousspeeds.
Breeder reacor: A nuclear reactor that produces morefuel than it consumes.
Critical mass: The mass of fissionable material that/ must
be availablefor a reaction to be self-sustainr g.
Deuterium: An isotope of hydrogen, containing one eutron.
ElectrOn capture: A nuclear reaction in which an tectronis captured by the nucleus.
Gamma rays: Electromagnetic radiation of very short wave-
length.
Geiger counter: A device for,measuring radiation.
Half-life: The time required for half of a given quantity
-of radioactive substance to decay.
Neutron: Neutral particle found in the nucleus of an atom.
Nuclear chemistry: The branch of chemistry dealing withatoms that contain unstable nuclei.
Nuclear fission: A process in which a large atom. is splitinto' smaller fragments.
Nuclear fusion: The process in which light atoms combine,to form heavier atoms; with a release of tremendousamounts of energy.
Nucleus: The inner core of an atom. '
Positron: 'A particle that has the same mass of an electron,but a positive charge.
Pr,-,ton: Positively charged particle found in the. nucleus
of an atom.
Radioisotopes: Radioactive substances widely used in medi-cihe and'industry.
Tritium: An isotope of hydrogen, containing two neutrons,
250CH-II/Page 33